Sample paper -1

Class 12^{th}

Physics (Theory) Term-2

M.M: 35 TIME-2Hrs

Here Physics classes by Nayan jha providing CBSE Term-2 Physics sample paper .

There are 12 questions in all and all questions are compulsory.

This question paper consists of three section A,B and C.

SECTION A has three questions of two marks each ,

SECFTION- B there are eight questions carrying three marks each and

SECTION- C is case study based questions of five marks.

There is no overall choice . However , an internal choice has been provided.

Uses of calculator is not allowed.

SECTION-A

1. Find the ratio of energies of photons produced due to transition of electron of hydrogen atom from its (i) Second permitted energy level to the first level and, (ii) the highest permitted energy level .

Or,

The ground state energy of hydrogen atom is -13.6eV. What is the kinetic and potential energy of electron in this orbit.

2. Draw the circuit diagram showing the biasing of an LED . State the factor which controls (i) Wavelength of light (ii) intensity of light emitted by the diode.

3. Write the photoelectric equations of Einstein . Write two basic features of photon picture of electromagnetic radiation on which Einstein’s photoelectric equation is based.

SECTION-B

4. Draw V-I characteristics of p-n junction diode (i) When diode is reversed bias and (ii) when diode is forward biased . Explain why the current under reverse bias is almost independent of the applied voltage up to the critical voltage?

5.State the necessary conditions for producing total internal reflection of light. Draw the diagram to show how specially designed prism make use of T.I.R to obtained inverted image of the object by deviating rays (i) through 90^{0} and (ii) Through 180^{0}.

Or,

Three rays of light red , green and blue is fall normally on one of the equal side of an isosceles right angled prism . The refractive index of these rays are 1.39,1.44,1.47 respectively . Find which of these rays get internally reflected from diagonal side . Trace the path of rays . Justify your answer with necessary conditions.

6. 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 .

Or,

Draw a labelled diagram of alpha particle scattering experiment. Give Rutherford observations and discuss the significance of this experiment .

7. 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.

Or,

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.

8. 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 .

9. I n a single slit diffraction experiment , deduce the conditions for the central maximum and secondary maxima/minima observed in diffraction pattern . Also explain why the secondary maxima go on becoming weaker in intensity as the order increases. Haw does the width of the slit affected the size of the central bright fringe?

10. Using Young’s double slit experiment obtain the conditions for gating bright and dark fringes also derive the expression for the fringe width. Also write the effect on fringe width when(I)Distance between slits increases/decreases (II) Distance between slits and the screen increases/decreases(III) Monochromatic light replaced by white light,(IV) One of slit is closed and (V) entire experimental apparatus is immersed in a liquid.

11. (i) Which segment of electromagnetic waves has highest frequency? How are these waves produced? Give one use of these waves.

(ii) Which EM waves lie near the high frequency end of visible part of EM spectrum? Give its one use. In what way this component of light has harmful effects on humans?

Section-C

12.

**Power of a lens-**

Power (P) of a lens is given as the reciprocal of focal length (P=1/f)where f should be in meter and P is in Diopter . for convex power is positive and concave power is –ve. When two or more lenses are kept in contact then power of the combined lens is given as P= P_{1} + P_{2}+P_{3} …….

(I) A convex and a concave lens is separated by distance d are then put in contact then the focal length of the combination (a) becomes 0 (b) remain the same (iii) decreases (iv)increases.

(ii)The two lenses of power +1.5D and +1.0D are placed in contact then the effective power of the combination will be (a)2.5D (b)1.5 D (c) 0.5D (d)3.25D .

(iii) If the power of the lens is 5D then what is the focal length of the lens?(a)10cm (b) 20cm (c)15cm (d) 5cm

(iv)Two thin lens of focal length +10cm and -5cm are kept in contact , the power of the combination is ? (a)-10D (b)-20D (c)10D (d)15D .

(v)A convex lens of focal length 25cm is placed coaxially in contact with a concave lens of focal length 20cm the system will be ; (a) converging in nature (ii) diverging in nature (c) can be converging or diverging (d) None of the above.