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Category: 12th Assignments

Objective questions of capacitance
Objective questions of capacitance

This assignment contains all important objective questions of capacitance, it will be beneficial for the students preparing for class 12th board examination or preparing for JEE/NEET.

Before to solve this assignment student must solve the assignment of its previous chapter electric field and potential, to download the assignment of objective questions of electric field and potential click here.

Capacitance
1. There are 27 drops of a conducting fluid. Each has a radius r and they are charged to a potential V₀. These are combined to from a bigger drop. Its potential will be:
- (a)V₀ (b) 3V₀ (c) 9V₀ (d) 27V₀
1. 1000 small water drops each of radius r and charge q coalesce together to from one spherical drop. The potential of the bigger drop is larger than that of the smaller one by a factor:
- (a)1000 (b) 100 (c) 10 (d) 1
1. The capacitance of a parallel plate condenser does not depend upon:
- (a)area of the plates
- (b)medium between the plates
- (c)distance between the plates
- (d)metal of the plates
1. The force between the plates of a parallel plate capacitor of capacitance C and distance of separation of the plates d with a potential difference V between the plates is:
- (a)CV²/2d (b) C²V²/2d² (c) C²V²/d² (d) V²d/C
1. A parallel plate capacitor is made by stacking n equally spaced plates connected alternately. If the capacitance between any two plates is C, then the resulting capacitance is:
- (a)C (b) nC (c) (n-1)C (d) (n+1)C
1. Two parallel metal plates carry charge +Q and -Q respectively. A test charge q₀ placed between them experiences a force F. Now the separation between the plates is doubled, then the force on the test charge will be:
- (a)F (b) 2F (c) F/2 (d) F/4
1. A 2μF capacitor is charged to a potential of 200 V and then isolated. When it is connected in parallel with a second capacitor which is uncharged, the common potential becomes 40 V. The capacitance of the second capacitor is:
- (a)2μF (b) 4μF (c) 8μF (d) none of these
1. Three capacitors of capacitance 12μF each are available. The minimum and maximum capacitance which may be obtained from these are:
- (a)12μF, 36μF (b) 4μF, 12μF (c) 4μF, 36μF (d) 0μF, ꚙμF
To download entire assignment of objective questions of electric field click here -objective questions of Capacitance

To solve the assignment of important objective questions of electric current click here.

electric- current
December 27, 2019
Objective questions of alternating current
Objective questions of alternating current

This assignment (Objective questions of alternating current),provide the important objective questions of the chapter alternating current ,which is important for the students preparing for class-12th board examination or , other competitive examinations (JEE/NEET)

Before to solve this assignment (Objective questions of alternating current), student should solve the assignment of objective questions of electromagnetic induction-
1. A direct current of 5 amp is superimposed on an alternating current I = 10sin ɷt flowing through a wire. The effective value of the resulting current will be:
- (a)(15/2) amp (b) 5√3 amp (c) 5√5 amp (d) 15 amp
1. In an AC circuit, a resistance of R ohm is connected in series with an inductance L. If phase angle between voltage and current is 45°, the value of inductive reactance will be:
- (a)R/4
- (b)R/2
- (c)R
- (d)cannot be found with the given data
1. Resonance frequency of L – C circuit is:
- (a)1/2π √LC (b) 1/2πLC (c) 1/2π √L/C (d) 1/2π √LC
1. In L-C-R series AC circuit, the phase angle between current and voltage is:
- (a)any angle between 0 and ± π/2
- (b)π/2
- (c)π
- (d)any angle between 0 and π
1. In an L-C-R circuit, the capacitance is made one-fourth, when in resonance, so that the circuit remains in resonance?
- (a)4 times (b) (1/4) times (c) 8 times (d) 2 times
TO download complete assignment of Objective questions of alternating Current- click here-
December 24, 2019
Objective questions of electromagnetic induction
Objective questions of electromagnetic induction-

This assignment contains Objective questions of electromagnetic induction, which will help the students to prepare for class 12th board examination and other competitive exams like JEE/NEET.

Before to solve this assignment students has to solve assignment of magnetic effect of current, to solve the questions of magnetic effect of current click here
1. Lenz’s law is a consequence of the law of conservation of:
- (a)charge (b) mass (c) momentum (d) energy
1. The law of electromagnetic induction have been used in the construction of a:
- (a)galvanometer (b) voltmeter (c) electric motor (d) generator
1. A cylindrical bar magnet is kept along the axis of a circular coil. On rotating the magnet about the axis, the coil will have induced in it:
- (a)a current (b) no current (c) only an em (d) both an emf and a current
1. A horizontal straight conductor when placed along south-north direction falls under gravity; there is:
- (a)an induced current from south to north direction
- (b)an induced current from north to south direction
- (c)no induced emf along the length of the conductor
- (d)an induced emf along the length of the conductor
1. A car moves on a plane road. Induced emf produced across the axle is maximum when it moves:
- (a)at the poles (b)moves at equator (c) remains stationary
- (d) no emf is induced at all
To download complete assignment of objective questions of electromagnetic induction click here-Electromagnetic Induction

after solving this assignment of objective questions of electromagnetic induction student should solve the assignment of objective questions of alternating current . To download the complete assignment of objective questions of alternating current click here –
December 24, 2019
Objective questions of magnetism and matter
Objective questions of magnetism and matter

This assignment contains all type objective questions of magnetism and matter. it will be helpful for the students preparing for class 12th board examination or other competitive examinations like JEE/ NEET .

Magnetism and matter
1. With the tangent galvanometer it is desirable to have a deflection near 45°; then the percentage error:
- (a)is less in the reading of deflection
- (b)is negligible in the reading of deflection
- (c)is less in the measurement of current
- (d)is large in the measurement of current
1. The sensitivity of a moving coil galvanometer depends on:
- (a)the angle of deflection
- (b)the earth’s magnetic field
- (c)torsional constant of the spring
- (d)the moment of inertia of the coil
1. An ammeter can be converted into a voltmeter by connecting:
- (a)a high resistance in series
- (b)a low resistance in parallel
- (c)a low resistance in series
- (d)a high resistance in parallel
1. In a moving coil galvanometer the deflection of the coil θ is related to the electric current I by the relation:
- (a)I ꭀ tan θ (b) I ꭀ θ (c) I ꭀ θ² (d) I ꭀ √θ
1. A voltmeter of range 2V and resistance 300 Ω cannot be converted into ammeter of range:
- (a)1 A (b) 1 mA (c) 100 mA (d) 10 mA
1. The effect due to uniform magnetic field on a freely suspended magnetic needle is as follows:
- (a)both torque and net force are present
- (b)torque is present but no net force
- (c)both torque and net force are absent
- (d)net force is present but not torque
1. A voltmeter has a resistance of G ohm and range V volt. The value of resistance used in series to convert it into voltmeter of range nV volt is:
- (a)nG (b) (n – 1)G (c) G/n (d) G/(n – 1)
1. An ammeter has a resistance of G ohm and a range of I The value of resistance used in parallel to convert it into an ammeter of range nI amp is:
- (a)nG (b) (n – 1)G (c) G/n (d) G/(n – 1)
1. To reduce the range of a voltmeter, its resistance need to be reduced. Which of the following resistance when connected in parallel will convert it into a voltmeter of range (V/n)?
- (a)nR₀(b) (n + 1)R₀ (c) (n – 1)R₀ (d) None of these
To download entire assignment click here- Magnetism and matter objective
December 22, 2019
Objective questions of magnetic effect of current
Objective questions of magnetic effect of current

this assignment contains all important objective type questions of magnetic effect of current . Students preparing for 12th board examination or other competitive examination like JEE/NEET.

Before to solve objective questions of this chapter student may solve the objective questions of electric current. To download assignment of objective questions of electric current click here-
1. Magnetic induction is measured in:
- (a)weber (b) weber/m (c) weber/m² (d) weber/m³
1. The force acting on a charge q moving with a velocity ʋ in a magnetic field of induction B is given by:
- (a) q/(ʋ ₓ B) (b) (ʋ ₓ B)/q (c) q/(ʋ ₓ B) (d) (ʋ . B)q
1. Two free parallel wire carrying currents in the opposite directions:
- (a)attract each other
- (b)repel each other
- (c)do not affect each other
- (d)get rotated to be perpendicular to each other
1. Two parallel wires carrying currents in the same direction attract each other because of:
- (a)potential difference between them
- (b)mutual inductance between them
- (c)electric forces between them
- (d)magnetic force between them
1. A free charged particle moves through a magnetic field. The particle may undergo a change in:
- (a)speed (b)energy (c) direction of motion (d) none these
1. An electron and a proton travel with equal speeds and in the same direction, at 90° to a uniform magnetic field. They experience forces which are initially:
- (a)in opposite direction and differing by a factor of about 1840
- (b)in the same direction and differing by a factor of about 1840
- (c)equal but in opposite directions
- (d)identical
- To download complete assignment of magnetic effect of current CLICK HERE-
- TO download complete assignment of magnetism and matter click here-
December 22, 2019
Objective questions of current electricity
OBJECTIVE QUESTIONS OF CURRENT

This topic provide important objective questions for electric current it will be very important for the students preparing for class 12th board examination or JEE/NEET
1. For which of the following dependence of drift velocity ʋ on electric field E is ohm’s law obeyed?
- (a) ʋ ꭀ E (b) ʋ = constant (c) ʋ ꭀ E^1/2 (d) ʋ ꭀ E²
1. in metals the time of relaxation of electrons:
- (a)increases with increasing temperature
- (b)decreases with increasing temperature
- (c)does not depend on temperature
- (d)changes suddenly at 400 K
1. Constantan wire is used for making standard resistance because it has:
- (a)low specific resistance
- (b)high specific resistance
- (c)negligible temperature coefficient of resistance
- (d)high melting point
1. A potential difference is applied across the ends of a metallic wire. If the potential difference is doubled, the drift velocity:
- (a)will be doubled (c) will be quadrupled
- (b)will be halved (d) will remain unchanged
1. The maximum current that flows in the fuse wire, before it blow out, varies with the radius r as:
- (a)r^3/2 (b) r (c) r^2/3 (d) r^1/2
- To download entire questions paper click here-click here electric current objective questions
December 19, 2019
Objective questions of atoms and nuclei
This assignment contain all important objective questions of atoms and nuclei , which is important for the students preparing for board examination and other competitive examinations .

Atomic Structure
1. According to Bohr’s atomic model:
  (a)an atom has heavy, positively charged nucleus
  (b)the electron radiates energy only when it jumps to another orbit
  (c)the electron can move only in particular orbits
  (d)all the above statements are correct
1. In an atom, two electrons move around the nucleus in circular orbit of radii R and 4R. The ratio of the time taken by them to complete one revolution is:
  (a)1/4 (b) 4/1 (c) 8/1 (d) 1/8
1. According to Bohr’s quantum condition, an electron can revolve only in those orbits in which:
  (a) its energy is an integral multiple of h/2π
  (b) its linear momentum is an integral multiple of h/2π
  (c) its angular momentum is an integral multiple of h/2π
  (d) its angular momentum vector is perpendicular to magnetic dipole moment vector
1. According Bohr’s theory the radius of the electron in an orbit described by principal quantum number n and atomic number Z is proportional to:
  (a)Z²n² (b) Z²/n²
  (c) Z²/n
  (d) n² /Z
1. When the electron jumps from a level n = 4 to n = 1, the momentum of the recoiled hydrogen atom will be:
  (a)5 ₓ 10^-27 kg – ms^-1
  (b) 13.6 ₓ 10^-19 kg – ms^-1(c)75 ₓ 10^-19 kg – ms^-1
  (d) zero
1. The radius of Bohr’s fast orbit is a₀. The electron in nth orbit has a radius:
  (a)na₀
  (b) a₀/n
  (c) n²a₀
  (d) a₀/n²
1. The angular momentum of an electron in the nth orbit is given by:
  (a)nh
  (b) h/2πn
  (c) nh/2π
  (d) n²h/2π
1. When a hydrogen atom is raised from the ground state to fifth state:
  (a)both KE and PE increase
  (b) PE increases and KE decreases
  (c)both KE and PE decrease
  (d) PE decreases and KE increases
2. As the electron in Bohr orbit of hydrogen atom passes from state n = 2 to n = 1, the KE (K) and PE (U) change as: (a)K two-fold, U also two-fold
  (c) K four-fold, U two-fold
  (b)K four-fold, U also four-fold
  (d) K two-fold U four-fold
3. An electron jumps from the 4^th orbit to the 2^nd orbit of a hydrogen atom. Given the Rydberg constant R = 10⁵ cm^-1, the frequency in Hz of the emitted radiation will be:
  (a)3/16 ₓ 10⁵
  (b) 3/16 ₓ 10¹⁵
  (c) 9/16 ₓ 10¹⁵
  (d) 3/4 ₓ 10^¹⁵
4. Nitrogen gas, cynogen gas and compounds of carbon give band spectra because:
  (a)these are excited in molecular state
  (b)these are in atomic state
  (c)these are inorganic compounds
  (d)these are in gaseous state
5. The hydrogen atom can give spectral lines in the series, Lyman, Balmer and Paschen. Which of the following statements is correct?
  (a)Lyman series is in the infrared region
  (b)Balmer series is in the visible region (partly)
  (c)Balmer series is solely in the ultraviolet region
  (d)Paschen series is in the visible region
6. .Which of the following statements is true regarding Bohr’s model of hydrogen atom?
  (a)Orbiting speed of electron decreases as it falls to discrete orbits away from the nucleus.
  (b)Radii of allowed orbits of electrons are proportional to the principal quantum number.
  (c)Frequency with which electrons orbits around the nucleus in discrete orbits is inversely proportional the principal quantum number.
7. Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits.
  
  (A)a and    c
  (B)   b    and    d
  (C)   a, b   and   c
  (D)   b, c   and   d
8. An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photo-electron is 10 V, then the value of n is:
  (a)2 (b) 3 (c) 4 (d) 5
9. In Bohr’s model, the atomic radius of the fast orbit is r₀;then the radius of the third orbit is:
  (a)r₀/9 (b) r₀ (c) 9r₀ (d) 3r_₀
10. The ground state energy of H-atom is 13.6 eV. The energy needed to ionise H-atom from its second excited state is: (a)51 eV (b) 3.4 eV (c) 13.6 eV (d) 12.1 eV
11. Hydrogen atoms are excited from ground state to the state of principal quantum number 4. Then, the number of spectral lines observed will be:
  (a) 3 (b) 6 (c) 5 (d) 2
12. If an electron in n = 3 orbit of hydrogen atom jumps down to n = 2 orbits, the amount of energy released and the wavelength of radiation emitted are:
  (a)85 eV, 6566 Å (b) 1.89eV, 1240 Å (c) 1.89 eV, 6566 Å (d) 1.5 eV,6566 Å
13. The longest wavelength that a single ionised helium atom in its ground state will absorb is:
  (a)912 Å (b) 304 Å (c) 606 Å (d) 1216 Å
14. If the ionisation potential of hydrogen atom is 13.6 eV, the energy required to remove the electron from the third orbit of hydrogen atom is:
  (a)5 V (b) 1.5 eV (c) 4.5 eV (d) 3.4 V
15. The ratio of the areas within the electron orbits for the first excited state the ground state for the ground state for the hydrogen atom is:(a)2 : 1 (b) 4 : 1 (c) 8 : 1 (d) 16 : 1
16. The first excitation potential of the hydrogen atom in the ground state is:
  (a)6 volt (b) 10.2 volt (c) 3.4 volt (d) 1.89 volt
17. The minimum energy in electron volt required to strip a ten times ionized sodium atom ( i.e., Z = 11) of its last electron is:
  (a)6 eV (b) 13.6/11 eV (c) 13.6 ₓ 11 eV (d) 13.6 ₓ (11)² eV
18. Of the following transitions in hydrogen atom, the one which gives emission line of minimum frequency is:(a)n = 1 to n = 2 (b) n = 3 to n = 10 (c) n = 10 to n = 3 (d) n = 2 to n = 1
19. The energy of an electron in the nth orbit of positronium is:
  (a) -13.6/n² eV (b) -13.6 ₓ 2/n² eV (c) -13.6 ₓ 4/n² eV (d) -13.6/2n²eV
20. The ratio (in SI units) of magnetic dipole moment to that of the angular momentum of electron of mass m kg and charge e coulomb in Bohr’s orbit of hydrogen atom is:
  (a) e/2m (b) e/m (c) 2e/m (d) none of these
21. The Bohr model of atoms:
  (a)assumes that the angular momentum of the electrons is quantized
  (b)uses Einstein’s photoelectric equation
  (c)predicts continuous emission spectra for atoms
  (d)predicts the same emission spectra for all types of atoms
22. The angular momentum of an electron in a hydrogen atom is proportional to:
  (a)1/√r (b) 1/r (c) √r (d) r^²
23. What will be the angular momentum in fourth orbit, if L is the angular momentum of the electron in the second orbit of hydrogen atom?
  (a)2 L (b) 3/2 L (c) 2/3 L (d) L/2
24. The required energy to detach one electron from Balmer series of hydrogen spectrum is:
  (a)6 eV (b) 10.2 eV (c) 3.4 eV (d) -1.5 eV
25. Which of the following is quantised according to Bohr’s theory of hydrogen atom? (a)Linear momentum of electron
  (b)Angular momentum of electron
  (c)Angular velocity of electron
  (d)Linear velocity of electron
26. The energy levels of a certain atom for 1^st ,2^nd and 3^rd levels are E, 4E/3 and 2E respectively. A photon of wavelength λ is emitted for a transition 3 →1.What will be the wavelength of emission for transition 2 → 1?
  (a) λ/3 (b) 4λ/3 (c) 3λ/4 (d) 3λ
27. The ratio of the frequencies of the long wavelength limits of the Lyman and Balmer series of hydrogen is:
  (a)27 : 5 (b) 5 : 27 (c) 4 : 1 (d) 1 : 4
28. If electron in a hydrogen atom has moved from n = 1 to n = 10 orbit, the potential energy of the system has:
  (a)Increased (b)Decreased (c) remains unchanged (d) become zero
29. The energy of hydrogen atom in nth orbit is E_n , then the energy in nth orbit of singly ionised helium atom will be:
  (a)4E_n (b) E_n/4 (c) 2E_n (d) E_n/2
30. The energy of hydrogen atom is -13.6 eV in the first orbit, then calculate the energy of He atom in the same orbit:
  (a)6 eV (b) -27.2 eV (c) -54.4 eV (d) +54.4 eV
31. In hydrogen spectrum, the shortest wavelength in Balmer series is λ. The shortest wavelength in Brackett series will be:(a)2λ (b) 4λ (c) 9λ (d) 16λ
32. The ratio of the largest to shortest wavelength in Lyman series of hydrogen spectra is:
  (a) 25/9 (b) 17/6 (c) 9/5 (d) 4/3
33. The minimum orbital angular momentum of the electron in hydrogen atom is:
  (a) h (b) h/π (c) h/2π (d) h/2
34. The total energy of an electron in the first excited state of hydrogen atom is about – 3.4 eV. Its KE in this state is:
  (a)4 eV (b) 6.8 eV (c) -3.4 eV (d)-6.8 eV
35. The ground state energy of hydrogen atom is -13.6 eV. What is the potential energy of the electron in this state?
  (a)0 eV (b) -27.2 eV (c) 1 eV (d) 2 eV
36. If λ₁ and λ₂ are the wavelengths of the first member of the Lyman and Paschen series respectively, then λ₁ : λ₂ is:
  (a)1 : 3 (b) 1 : 30 (c) 7 : 50 (d) 7 : 108
November 13, 2019
Objective questions of wave optics
Objective questions of wave optics

diffraction central maximum

Student’s as we know from this year , in CBSE 12th board examination ( physics ) there will be 20 , 1- mark questions . therefore we just posted some objective questions of wave optics , so that students can practice well all kind of objective questions of wave optics in short time .

Objective questions of wave optics
1. Newton has postulated his corpuscular theory on the basis of , (a) Newton’s ring (b) color due to thin film (c) dispersing of light (d) rectilinear propagation of light.
2. The wavefront is a surface in which ; (a) all points are on the same phase(b) there are pair of points in opposite phase (c) there are pairs of points with phase difference 90⁰ (d)there are no relation between the phase.
3. The concepts of secondary wavelets from all points on a wave front was proposed by ; (a) Newton (b) Huygen (c) Faraday (d) Raman.
4. Huygen’s concepts of secondary waves ; (a) allow us to find the focal length of thin lens (b) gives the magnifying power of thin lens (c) is a geometrical method to find the wavelength (d)is used to find the velocity of light.
5. For constructive interference to take place between two monochromatic light waves of wavelength λ , the path difference should be ; (a) (2n-1)λ/4 (b) (2n-1)λ/2 (c) nλ (d)(2n+1)λ/2
6. Two light sources are coherent when ; (a) their amplitudes are equal (b) their frequency are equal (c) their wavelengths are equal (d)their frequencies are equal and their phase difference is constant.
7. Ratio of intensity of two waves is given by 4:1 , the ratio of amplitudes of their waves is ; (a) 2:1 (b)1:2 (c) 4:1 (d)1:4
8. If the ratio of intensities of two waves causing interference be 9:4 then the ratio of the resultant maximum and minimum intensity will be : ; (a) 9:4(b) 3:2 (c) 25:1 (d)5:1 .
TO SOLVE IMPORTANT QUESTIONS ( THEORY AND NUMERIALS)-CLICK HERE
1. In young’s double slit experiment , if monochromatic light used is replaced by white light , then ; (a) no fringes are observed (b) all bright fringes becomes white (c) all fringes have colour between violet and red (d)only central fringes is white and all other fringes are coloured .
2. Two coherent monochromatic light beams of intensity I and 4I are superposed , the max and min. possible intensities in the resulting beam are ; (a) 5I and I (b) 5I and 3I (c) 9I and I (d) 9I and 3I
3. If two waves , each of intensities I₀ , having the same frequency but differing by constant phase angle of 60⁰ , superpose at a certain point in space , then the intensity of resultant wave is ; (a) 2I₀ (b) √3 I₀ (c) 3I₀ (d) 4I₀
4. Two monochromatic waves each of intensity I , have constant phase difference of ɸ , if these waves superpose , then the intensity of resulting wave is ; (a) 4I (b) 4Icosɸ (c) 4Icos²ɸ (d) 4I cos²(ɸ/2)
5. Two monochromatic waves of same amplitude ‘a’ ,have random phase difference between them . when these wave superpose , then the amplitude of resulting wave is given by ; (a) √2a (b) 2a (c) 4a (d)zero .
6. The contrast in the fringes in any interference pattern depends on ; (a) fringe width (b)wavelength (c) intensity ratio of the sources (d) distance between the sources
7. In young’s double slit experiment if the distance between the slits is made 3-folds, the fringe width becomes ; (a) 1/3 folds (b) 3 folds (c) 1/9 folds (d) 9 folds .
8. In Young’s double slit experiments the separation between the is halved and separation between the slits and screen is doubled , the fringe width is ; ; (a) unchanged (b) halved (c) doubled (d) quadrupled .
9. Yellow light emitted by sodium lamp in Young’s double slit experiment is replaced by blue light of the same intensity ; (a) fringe width will decrease (b) fringe width will increase (c) fringe width will remain unchanged (d) fringe will become less intense .
10. Two light waves are coherent if they are obtained from a single monochromatic source by ; ; (a) division of amplitude only (b) division of wavefront only (c) both of the above (d) none of the above.
TO SOLVE IMPORTANT QUESTIONS OF RAY OPTICS – CLICK HERE
1. In an interference experiment monochromatic light is replaced by white light , we will see , ; (a) uniform illumination on the screen (b) uniform darkness in the screen (c) equally spaced white and dark bands (d) a few coloured bands and then uniform illumination .
2. In Young’s double slit experiment the fringe width is found to be 0.4 mm . if the whole apparatus is immersed in water of refractive index 4/3 without disturbing the original geometric arrangement , then new fringe width will be ; (a) 0.3mm (b)0.40mm (c) 0.53mm (d )450 microns .
3. Two waves are said to be coherent if they have ; (a) same wave length (b) same amplitude (c) same amplitude and save wavelength (d) same wavelength and constant phase difference .
4. In a young’s double slit experiment fringe width is equal to 1mm , then the distance of the nearest bright fringe from the central fringe will be ; (a) 1mm (b) 0.5mm (c) 2mm (d) insufficient data ,
5. In young’s double slit experiment . if width of the slit s is increased keeping other parameters constant , then the interference fringes will be ; (a) remain unchanged (b) form closer (c) form further away (d) gradually disappear.
6. Interference of light waves from two coherent sources is possible for ; (a) unpolarised light waves only (b) polarised light waves only if their polarisation is in the same direction (c) both of the above (d) none of the above.
7. Two waves coming from two coherent sources , having different intensity interfere , their ratio of maximum intensity is 25 , then the intensities of the sources are in the ratio ; (a) 25:1 (b) 25:16 (c) 9:4 (d) 5:1 .
8. When petrol drop from a vehicle fall over rain water on the road , colors are seen because of ; (a) dispersion of light (b) scattering of light (c) interference of light (d) absorption of light.
9. In one of the two slits of young’s double slit experiment is painted over so that it transmits half the light intensity of the other , then ; (a) the fringe system will disappear (b) the bright fringe will be more bright (c) the dark fringe will be brighter and vice -versa (d) none of the above .
10. The phenomena of diffraction can be exhibited by ; (a) polarised wave only (b) unpolarised wave only (c) longitudinal wave only (d)all kind of wave
11. Diffraction effects are easily observed for ; (a) microwave (b) sound wave (c) radio waves (d) all of the these .
12. In case of diffraction at single slit if the wavelength of light becomes equal to the aperture of slit , on the screen we shall observe : ; (a) image of slit (b) diffraction band (c)uniform illumination (d) non-uniform illumination.
13. Light of wavelength 2 x 10^-3 m falls on a slit of width 4 x 10^-3 m . the angular dispersion of the central max will be ; (a) 30⁰ (b) 60⁰ (c) 90⁰ (d) 180⁰ .
14. The width of the diffraction band varies as (a) inversely as the wavelength (b) directly as the width of the slit (c) directly as the distance between slit and the screen (d) inversely as the size of source from which the slit is illuminated .
15. The polarisation of light prove the ; (a) corpuscular nature of light (b) quantum nature of light (c) transverse wave nature of light (d) longitudinal wave nature of light .
16. A beam of light strikes a piece of glass at an angle of incidence of 60⁰ and reflected beam is completely plane polarized , then the refractive index of glass is ; (a) 1.5 (b) √3 (c) √2 (d) 2/3.
17. A ray of light incident on the surface of a glass plate at an angle of incidence equal to Brewster’s angle ɸ. If µ is the refractive index of the glass then the angle between reflected and refracted rays is ; (a) (90+ɸ) (b) sin^-1 (µ cosɸ) (c) 90⁰ (d) sin^-1( sinɸ/µ).
18. A Nicol prism is based on the principle of ; (a) refraction (b) scattering (c) dichroism (d) double refraction .
19. Which of these wave can be polarised ? (a)sound wave (b) longitudinal wave on a string (c) transverse wave on a string (d) light wave
20. Two Nicol prism are first crossed and ten one of them is rotated through 60⁰ , the percentage of incident light transmitted is ; (a) 1.25 (b)25 (c)37.5 (d)50 .
21. Two polaroids are placed cross to each other , now one of them is rotated through an angle of 45⁰ the percentage of incident light now transmitted through the system is (a)15% (b)25% (c) 50% (d) 60% ( e) 75%.
22. Waves can’t be polarised is ; (a) light wave (b) electromagnetic wave (c) transverse wave (d) longitudinal wave .
23. Young’s double slit experiment is made in a liquid . The tenth bright fringe in the liquid lies where the 6^th bright fringe lies in the vacuum . The refractive index of the liquid is approximately ; (a) 1.8 (b) 1.54 (c) 1.67 (d) 2 .
24. If light is polarised by reflection , then the angle between reflected and refracted light is ; (a) Π (b) Π/2 (c) Π/3 (d) Π/4
25. A beam of light strikes a piece of glass at an angle of incidence of 60⁰and the reflected ray is completely polarised . Then the refractive index of the glass is ; (a) 1.5 (b) √3 (c) √2 (d)3/2
26. What does not change on polarisation of light ; (a) intensity (b) phase (c) frequency (d) wavelength TO SOLVE OTHER IMPORTANT QUESTIONS OF WAVE OPTICS – CLOCK HERE
October 8, 2019
Important questions of dual nature of radiation and matter
Important questions of dual nature of radiation and matter

Dual nature

In this assignment, important questions of dual nature of radiation and matter , i am trying to provide some important questions based on the chapter dual nature of radiation and matter, student preparing for 12th board exam must solve all the questions , this chapter is little bit easier than other previous chapter of physics class 12th.Numerical based on this chapter is bit easier than other chapters, so prepare this chapter nicely , and solve all the questions , i am sure that students will get benefit from this assignment of important questions of dual nature of radiation and matter.

Dual nature of matter and radiation
1. List important observations made by Lenard which lead to quantum theory of radiations .
2. State De-Broglie hypothesis . Derive an expression for the De-Broglie wavelength associated with an electron accelerated through a potential V . draw the schematic diagram of a localized-wave describe the wave nature of the moving electron .
3. Define the term threshold frequency and stopping potential in relation to the phenomenon of photoelectric effect . how is photoelectric current affected on increasing the (I) frequency (II) intensity of the incident radiations and why?
4. Sketch the graphs showing the variation of stopping potential with frequency of incident radiations for two photosensitive radiations for two photosensitive materials A and B having threshold frequencies ѵ₀ > ѵ₀^’ respectively . (I) which of the two metals ,A and B has higher work function ? (II) what information do you get from the slope of the graphs ? (III) what does the value of the intercept of graph A on the potential axis represent ? FOR IMPORTANT QUESTIONS OF RAY OPTICS -CLICK HERE
5. Draw the graphs showing the variation of photoelectric current with anode potential of a photocell for (I) the same frequencies but different intensities I₁ >I₂ > I₃ incident radiation, (II) the same intensities but different frequencies ѵ₁> ѵ₂ >ѵ₃of incident radiation . Explain why the saturation current is independent of the anode potential.
6. What is the photoelectric current ? Write Einstein’s photoelectric equation and use it to explain (I) independence of photoelectrons from intensity , of incident light , (II) Existence of threshold frequency for emission of photoelectrons. FOR IMPORTANT QUESTIONS OF WAVE OPTICS AND OPTICAL INSTRUMENT CLICK HERE
7. An electron of mass m and charge q is accelerated from rest through a potential difference V , obtain the expression for the de-Broglie wavelength associated with it . if electron and proton are moving with the same K.E. , which one of them will have a large De-Broglie wavelength associated with it ? give reason .
8. State the dependence of the work function on the K.E. of electrons emitted in a photocell . (a) if the intensity of the incident radiation increases to double of its initial intensity what change occur in the (I) stopping potential and (II)photoelectric current.(b) if the frequency of the incident radiation is doubled what change occur in the (I) stopping potential (II)photoelectric current(III) K.E. of the photo electron emitted
9. Given below in the graph between frequency of the incident light and maximum kinetic energy of the emitted photoelectron find the value of (I) threshold frequency and (II) work function from the graph.
  dual pic-1
10. In a photoelectric effect experiment , the graph between the stopping potential V and frequency v of the incident radiation on two different metal plate P and Q in the fig. (I) which of the two metal plates , P and Q has greater value of work function ?(II)what does the slope of the lines depict ?
  dual pic-2
11. Ultraviolet light of wavelength 2271 A from a 100W mercury source is incident on a photocell made of molybdenum metal , if the stopping potential is 1.3 V , estimate the work function of the metal.
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WHAT IS DIFFRACTION OF LIGHT ? TO KNOW COMPLETE ASSIGNMENT. CLICK HERE-
September 24, 2019
Important questions of atoms and nuclei
Important questions of atoms and nuclei.

This topic is important for class 12th student . it is considered this chapter is little bit easier than other previous chapter of physics for board examination point of view . One important reason is that student already studied this chapter in class 11th (chemistry) , so it is easy to learn this chapter . Through “important questions of atoms and nuclei” , I am going to provide some important questions based on this topic . Student preparing for board examination of all board should revise all these questions given in ” important questions of atoms and nuclei”.

ATOMS AND NUCLEI

Here is some important questions of atoms and nuclei-

Atoms- nuclei
1. Draw a labelled diagram of alpha particle scattering experiment. Give Rutherford observations and discuss the significance of this experiment .
2. Using postulates of Bohr energy of hydrogen atom ,show that (a) the radii of orbits increases as n² and (b) the total energy of the electron increases as 1/n² , where n is the principle quantum number of the atom .
3. Draw a schematic arrangement of the Gieger -Marsden experiment for studying alpha particle scattering by a thin foil of gold . describe briefly , by drawing trajectories of the scattered alpha particle . haw this studies can be used to estimate the size of the nucleus ?
1. State any two postulates of Bohr theory of hydrogen atom . what is the maximum possible no. of spectral lines observed when the hydrogen atom is in its second exited state ? justify your answer . calculate the ratio of the max. and min. wavelength of the radiation emitted in this process.
1. Using Bohr postulates for hydrogen atom , show that the total energy of the electron in the stationary states can be expressed as the sum of kinetic energy(K) and potential energy (U) , where K=-2U. hence , deduce the expression for the total energy in the n^th energy level of hydrogen atom .
1. The energy of an electron in the ground state of hydrogen atom is -13.6 Ev. (i) what does the negative sign signify ? (ii)how much energy is required to take an electron in this atom from the ground state to the first exited state?
1. In Bohr theory of hydrogen atoms, calculate the energy of the photon emitted during a transition of the electron from first exited state to its ground state . write in which region of the electromagnetic spectrum this transition lies. Given R=1.03 * 10⁷m^-1.
2. The electron in a given Bohr orbit has a total energy of -1.5Ev. calculate its(i) kinetic energy(ii)potential energy (iii) wavelength of the radiation emitted , when this electron makes a transition to the ground state.
3. The energy level diagram of an element is given below . identify using necessary calculations , which transition corresponds to the emission of the spectral line of wavelength 102.7 nm . which transition corresponds to the emission of radiation of maximum wavelength?
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atoms and nuclei
1. The ground state energy of hydrogen atom is -13.6 eV. ( I ) What is the potential energy of an electron in the third exited state? (ii) what will be the maximum and minimum wavelength of the emitted radiation of Lyman series of hydrogen spectrum.
1. State and explain the law of radioactive decay. Plot the graph of showing the number (N) of undecayed nuclei as a function of time (t) for a given radioactive sample having half life T_1/2.depict in the plot the number of undecayed nuclei at (i) t=3T_1/2 (ii) t=5T_1/2.
1. How the size of nuclei is experimentally determined ? write the relation between the radius and mass number of the nucleus . show that the density of the nucleus is independent of its mass number. Two nuclei of mass number in the ratio 27:125. What is the ratio of their nuclear radius and , ratio of their densities.
1. (i)Define the activity of the radioactive material and write its SI unit. plot a graph showing the variation of activity with respect to time of a given radioactive sample.(ii) what is meant by half life time of a radioactive element ? the half life of a radioactive sample is 30s calculate (a) the decay constant and (b)time taken for the sample to decay by 3/4^thof the initial value .explain alpha , beta and , gama decay with an example . if an element ²³⁸X ₉₂ converted into another element ²²²Y₉₀ find the no of alpha and beta particles emitted.
1. Draw the binding energy per nucleon curve . using the curve state clearly how the release in energy in the process of nuclear fission and nuclear fusion can be explained.
1. Draw a plot of potential energy of a pair of nucleons , as a function of their separation . write two important conclusions which you can draw regarding the nature of nuclear force. Also, explain the mass of a nucleus , in the ground state is always less than total mass of its constituents neutron and proton .
1. We are given the following atomic masses ; ²³⁸U₉₂=238.05079u;²³⁴Th₉₀=234.04363u ;²³⁷Pa₉₁=237.05121u;¹H₁=1.00783u;⁴He₂=4.00260 u ;(a) calculate the energy released during alpha decay of uranium (b) calculate the kinetic energy of alpha particle ,and (c) show that ; ²³⁸U₉₂cannot spontaneously emit a proton.
1. The activity of a radioactive sample drop to 1/16 ^th of its initial value in 32 years . find the mean life of the sample .
September 23, 2019