physics : class12 Saturation Current : Particle Nature of Light : Dual Nature of Matter and Radiation MCQ Questions and Answers
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Saturation Current
MCQ questions and answers.
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MCQ Questions
1. What is meant by saturation current in the photoelectric effect?
A.
The maximum current obtained when all emitted photoelectrons are collected
B.
The current obtained when no electrons are emitted
C.
The current at which the metal starts melting
D.
The current produced only by increasing the frequency of light
Correct Answer:
The maximum current obtained when all emitted photoelectrons are collected
Explanation:
Saturation current is the maximum photocurrent reached when the applied collecting potential is sufficient to collect all photoelectrons emitted from the metal surface.
2. What happens to the photocurrent when the applied collecting potential is increased beyond the saturation value?
A.
It becomes zero
B.
It decreases continuously
C.
It remains nearly constant
D.
It changes its direction
Correct Answer:
It remains nearly constant
Explanation:
Beyond the saturation potential, all emitted photoelectrons are already being collected, so further increase in potential does not increase the photocurrent.
3. For a fixed frequency of incident light, increasing its intensity generally causes the saturation current to:
A.
Increase
B.
Decrease
C.
Remain zero
D.
Become independent of the number of emitted electrons
Correct Answer:
Increase
Explanation:
Higher light intensity ejects more photoelectrons per second, so the maximum or saturation current increases.
4. The saturation current in a photoelectric experiment mainly depends on the:
A.
Number of photoelectrons emitted per second
B.
Mass of the metal plate only
C.
Colour of the connecting wires
D.
Size of the battery only
Correct Answer:
Number of photoelectrons emitted per second
Explanation:
Saturation current is the rate of collection of all emitted photoelectrons, so it depends on the number of photoelectrons emitted per second.
5. If the intensity of light falling on a photosensitive surface is doubled, while its frequency remains unchanged, the saturation current will generally:
A.
Increase
B.
Become exactly zero
C.
Remain unchanged in every case
D.
Reverse its direction
Correct Answer:
Increase
Explanation:
At unchanged frequency, doubling the light intensity generally increases the number of emitted photoelectrons and hence increases the saturation current.
6. Which condition is necessary for obtaining saturation current?
A.
All emitted photoelectrons must be collected by the collector
B.
No photoelectrons should reach the collector
C.
The light intensity must be zero
D.
The collector must be disconnected
Correct Answer:
All emitted photoelectrons must be collected by the collector
Explanation:
Saturation current is obtained only when the collecting electric field gathers all photoelectrons emitted from the photosensitive surface.
7. In a graph of photocurrent versus applied collecting potential, the saturation current is represented by the:
A.
Maximum constant value of photocurrent
B.
Point where photocurrent is always zero
C.
Minimum negative value of photocurrent
D.
Value obtained before any light is switched on
Correct Answer:
Maximum constant value of photocurrent
Explanation:
The saturation current is the plateau value of the photocurrent reached when increasing the collecting potential no longer increases the current.
8. If more intense light of the same frequency is used, the saturation current increases because:
A.
More photoelectrons are emitted per second
B.
Each photoelectron loses its charge
C.
The metal surface becomes an insulator
D.
The collector stops attracting electrons
Correct Answer:
More photoelectrons are emitted per second
Explanation:
For the same frequency, greater intensity means more incident photons per second, producing more emitted photoelectrons and a larger saturation current.
9. At saturation, the photocurrent is maximum because:
A.
The collection of photoelectrons is complete
B.
The light has stopped falling on the surface
C.
The photoelectric emission has stopped
D.
The circuit contains no source of potential
Correct Answer:
The collection of photoelectrons is complete
Explanation:
Once every emitted photoelectron is collected, the photocurrent cannot increase further and reaches its saturation value.
10. Which change will directly increase the saturation current in a photoelectric experiment?
A.
Increasing the intensity of incident light
B.
Decreasing the number of incident photons
C.
Blocking the incident light completely
D.
Removing the collecting electrode
Correct Answer:
Increasing the intensity of incident light
Explanation:
Increasing light intensity increases the number of photoelectrons emitted per second, thereby increasing the saturation current.
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