physics : class12 Light Intensity Effect : Particle Nature of Light : Dual Nature of Matter and Radiation MCQ Questions and Answers
Practice important
Light Intensity Effect
MCQ questions and answers.
Page 1
of
1
|
10
MCQ Questions
1. In the photoelectric effect, what happens to the number of photoelectrons emitted per second when the intensity of incident light is increased, while its frequency remains constant?
A.
It decreases
B.
It increases
C.
It becomes zero
D.
It remains unchanged
Correct Answer:
It increases
Explanation:
Increasing light intensity means more photons strike the metal surface per second. Therefore, more photoelectrons are emitted per second.
2. The photoelectric current from a metal surface mainly depends on the intensity of incident light when the frequency is above the threshold frequency. What happens when the intensity is increased?
A.
The photoelectric current increases
B.
The photoelectric current decreases
C.
The photoelectric current becomes zero
D.
The photoelectric current remains unchanged
Correct Answer:
The photoelectric current increases
Explanation:
Higher intensity provides more photons per second, producing more emitted electrons and hence a greater photoelectric current.
3. If the intensity of incident light is increased without changing its frequency, the maximum kinetic energy of photoelectrons:
A.
Increases
B.
Decreases
C.
Remains unchanged
D.
First increases and then becomes zero
Correct Answer:
Remains unchanged
Explanation:
The maximum kinetic energy of photoelectrons depends on the frequency of light, not on its intensity.
4. When the intensity of light is increased at a fixed frequency above the threshold frequency, the stopping potential:
A.
Increases
B.
Decreases
C.
Remains unchanged
D.
Becomes negative in every case
Correct Answer:
Remains unchanged
Explanation:
Stopping potential is determined by the maximum kinetic energy of photoelectrons. Since the frequency is unchanged, the stopping potential remains unchanged.
5. For light of frequency greater than the threshold frequency, which change is produced by increasing its intensity?
A.
Increase in the maximum speed of photoelectrons
B.
Increase in the number of photoelectrons emitted
C.
Decrease in the threshold frequency of the metal
D.
Decrease in the energy of each photon
Correct Answer:
Increase in the number of photoelectrons emitted
Explanation:
Increasing intensity increases the number of incident photons per second, so more photoelectrons are emitted. The energy of each photon remains fixed because frequency is unchanged.
6. The saturation current in a photoelectric experiment is increased by increasing the intensity of incident light because:
A.
More photoelectrons are emitted per second
B.
The work function of the metal increases
C.
The frequency of light increases automatically
D.
The stopping potential becomes larger
Correct Answer:
More photoelectrons are emitted per second
Explanation:
Saturation current is proportional to the rate of emission of photoelectrons. Greater intensity supplies more photons and increases this rate.
7. Two light beams have the same frequency above the threshold frequency, but beam X has greater intensity than beam Y. Which beam emits more photoelectrons per second from the same metal?
A.
Beam X
B.
Beam Y
C.
Both emit the same number in all cases
D.
Neither beam can emit photoelectrons
Correct Answer:
Beam X
Explanation:
At the same frequency, the more intense beam contains more photons per second. Thus, beam X emits more photoelectrons per second.
8. If the intensity of light is doubled while its frequency remains above the threshold frequency, the photoelectric current generally:
A.
Doubles
B.
Becomes half
C.
Remains zero
D.
Becomes independent of the number of emitted electrons
Correct Answer:
Doubles
Explanation:
For a fixed frequency above threshold, photoelectric current is proportional to light intensity. Therefore, doubling intensity approximately doubles the current.
9. Which quantity is not significantly changed by increasing the intensity of light at constant frequency in the photoelectric effect?
A.
Number of emitted photoelectrons per second
B.
Photoelectric current
C.
Maximum kinetic energy of photoelectrons
D.
Saturation current
Correct Answer:
Maximum kinetic energy of photoelectrons
Explanation:
The maximum kinetic energy depends on the frequency of light. Increasing intensity changes the number of emitted electrons, not their maximum kinetic energy.
10. Light of frequency above the threshold frequency falls on a metal. If its intensity is reduced, what happens to the photoelectric current?
A.
It increases
B.
It decreases
C.
It remains unchanged in every case
D.
It immediately changes the work function
Correct Answer:
It decreases
Explanation:
Lower intensity means fewer photons strike the metal per second, so fewer photoelectrons are emitted and the photoelectric current decreases.
Short Questions and Answers
Practice short questions and answers related to
Light Intensity Effect
.
Short questions are currently unavailable for this page.