This test paper d contain the questions of chapter, Dual nature and atoms and nuclei . Having completed these chapter students must try to solve this question paper. Provided by Nayan jha.
Physics classes by Nayan jha
Test class 12th
( Dual nature , Atoms and nuclei )
1. Draw a suitable graph to show the variation of photoelectric current with collector plate potential for (i) a fixed frequency but different intensities , I1>I2 > I3 of radiation .(ii) a fixed intensity but different frequencies v1 > v2 > v3 of radiations. [2marks] 2. Using De- Broglie hypothesis explain with the help of suitable diagram , Bohr’s second postulates of quantization of energy in hydrogen atom .. [2-marks] 3. Show that the density of nucleus over a wide range of nuclei is constant independent of mass number A. [2marks] 4. 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 . [3-marks] 5. 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 nth energy level of hydrogen atom . [3-marks] 6. . 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? [3-marks] 5.( Case study based question) Photoelectric effect is the phenomenon of emission of electrons from a metal surface , when radiation of suitable frequency fall on them . The emitted electrons are called photoelectrons and the current so produced is called photoelectric current. [5-marks] i. With the increase of intensity of incident radiation on photoelectrons emitted by a photo tube , the number of photoelectrons emitted pre unit time is (a) increases (b) decreases (c) remain the same (d) none of these ii. It is Observed that photoelectrons emission stops at a certain time t after the light source is switched on . The stopping potential can be represented as (a) 2(K.E.)max/e (b) (K.E.)max/e (c) (K.E.)max/3e (c) (K.E.)max/2e .
iii. A point source of light of power 3.2×10-3 W mono energetic photons of energy 5.0eV and work function 3.0eV . The efficiency of photoelectrons emission is 1 for every 106 incident photons . Assume that the photoelectrons are instantaneously swept away after emission . The max kinetic energy of photon is (a) 4eV (b) 5eV (c) 2eV (d) Zero .
iv. Which of the following is the application of photoelectric effect ? (a)L.E.D (b)Diode (c) Photocell (d) Transistor .
v. If the frequency of incident light falling on the photosensitive metal is doubled , the kinetic energy of the emitted photoelectrons is (a) Unchanged (b) halved (c) doubled (d) more than twice its initial value.