12th Assignments

Case study based questions on Photoelectric effect

Photoelectric effect

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.

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.

To solve the test based on the chapter Dual nature of matter . Atoms and nuclei, and Semiconductor devices click here-

Test Dual nature, Atoms Nuclei and semiconductor