# Photoelectric Effect Multiple Choice Questions And Answers

## Photoelectric Effect Definition

When light of suitable frequency is incident on a metal surface, electrons are emitted by the metal. This phenomenon is called ‘Photoelectric Effect’.

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## Photoelectric Effect Experiment

The experimental setup includes an evacuated chamber consisting of a metal electrode called ’emitter’, which can be illuminated by light of suitable frequency. Another electrode called ‘collector’ is situated at a distance from emitter.

Hertz’s and Lenard’s Observation regarding photoelectric effects is as follows:

• When UV radiations fall on emitter, electrons are ejected from it and are attracted towards positive collector plate.
• As soon as UV radiations are stopped, current flows stops.
• They studied the change in photo-current with change in collector plate potential, frequency and intensity of light.
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## Photoelectric Effect Equation

Einstein’s Photoelectric Equation is a short and crisp equation which summarizes all the relations in photoelectric effect.

$(KE)_{max}~=~ h\nu ~-~ W_0 ~=~ h(\nu~-~\nu_0) \\ \\ W_0 : Work~Function \\ \\ \nu_0 : Threshold~Frequency \\ \\ \nu : Frequency~of~incident~light$

## MCQ on electron and photons for class 12 physics.

The quiz on Photoelectric Effect and Multiple Choice Questions And Answers are as follows:

01. True or False: The maximum Kinetic Energy of photoelectrons increases with increase in frequency. It is independent of intensity

02. Energy & momentum of photons are independent of the _________ of incident radiation

03. True or False: The number of photoelectrons emitted per second (rate of photoelectrons emission) from a given metal is directly proportional to intensity. It is independent of frequency
05. In a photon-particle collision, the total energy and momentum are ____________04. True or False: In a photon-electron collision, one photon can eject two or more electrons

06. True or False: A bright monochromatic light mean more energetic photons are incident.

07. Stopping potential (in volts) is numerically equal to ________ of electron in eV

08. Momentum (p) of Photon p = ______

09. Maximum kinetic energy of photoelectron is _____________ Intensity of incident radiation
(a) directly proportional to
(b) inversely proportional to
(c) independent of
(d) directly proportional to square root of

10. Keeping frequency (which is more than threshold frequency) as constant, the photoelectric current is ________ intensity
(a) directly proportional to
(b) inversely proportional to
(c) independent of
(d) directly proportional to square root of

11. The minimum negative retarding potential to make photoelectric current zero, is called __________

12. True or False: Rest mass of photon is m = h / (cλ)

13. True or False: If the Frequency of incident radiation is kept constant but Intensity is changed, then Stopping potential remains same. However, saturation current increases with intensity

14. If the frequency of incident radiation is more than threshold frequency, the process of photoelectric effect takes place _____
(a) slowly
(b) rapidly
(d) instantaneously

15. The absorbed energy of incident photons is used in two ways:
(I). Work Function: part of energy is used to free the electron from metal surface and
(II). remaining part is converted to ____________
(a) kinetic energy
(b) potential energy
(c) binding energy
(d) thermal energy

16. True or False: In a photon-particle collision, photon may be absorbed in a collision or a new one created.

17. Maximum kinetic energy of photoelectron is _____________ Frequency of incident radiation
(a) directly proportional to
(b) inversely proportional to
(c) independent of
(d) directly proportional to square root of

18. Increase in ______ of incident radiation means more photons per unit area per second

19. True or False: Maximum Kinetic Energy of emitted electrons is independent of frequency and directly proportional to intensity of incident light

20. Photoelectric current is produced, when frequency of incident light is more than certain minimum frequency called ________________

21. Photoelectric Work Function (W0) for Mercury is ________ eV

22. At certain accelerating potential, all emitted electrons are collected by collector plate and photoelectric current is maximum. This is called __________

23. When light interacts with matter, it behaves like __________

24. If Frequency and Intensity of incident radiation are both kept constant, then photoelectric current ________ increase in positive accelerating potential
(a) decreases with
(b) increases with
(c) is independent of
(d) remains constant

25. True or False: Photons are electrically neutral and not deflected by electric or magnetic fields

26. If the frequency of incident radiation is more than threshold frequency, photoelectron emission starts in time order of _______ secs
(a) 1E-3
(b) 1E+3
(c) 1E-9
(d) 1E+9

27. Photons of same _______ have same energy & momentum

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01. True
02. intensity
03. True
04. False {One photon cannot eject more than one electron}
05. conserved
06. False {it mean more photons per unit area; and not more energetic photons}
07. kinetic energy
08. p = (hγ)/c = h/λ
09. (c) independent of
10. (a) directly proportional to
11. Cut-Off Potential or Stopping Potential
12. False {The above is the mass of moving photon. Rest mass is zero}
13. True
14. (d) instantaneously
15. (a) kinetic energy
16. True
17. (a) directly proportional to
18. intensity
19. False {Maximum Kinetic Energy of emitted electrons is directly proportional to frequency and independent of intensity of incident light}
20. Threshold Frequency (γ0)
21. 4.475 eV
22. Saturation Current
23. a particle
24. (b) increases with
25. True
26. (c) 1E-9
27. frequency