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# Test paper of Dual nature of matter and atoms and nuclei

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.