physics : class12 Threshold Frequency : Particle Nature of Light : Dual Nature of Matter and Radiation MCQ Questions and Answers
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Threshold Frequency
MCQ questions and answers.
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MCQ Questions
1. What is meant by the threshold frequency of a metal?
A.
The maximum frequency of incident light
B.
The minimum frequency of light required to emit photoelectrons
C.
The frequency of emitted photoelectrons
D.
The frequency at which light is completely absorbed
Correct Answer:
The minimum frequency of light required to emit photoelectrons
Explanation:
Threshold frequency is the minimum frequency of incident radiation needed to just eject photoelectrons from a metal surface.
2. If the frequency of incident light is less than the threshold frequency of a metal, photoelectric emission will:
A.
Take place immediately
B.
Take place after a long delay
C.
Not take place
D.
Take place only at high intensity
Correct Answer:
Not take place
Explanation:
Light with frequency below the threshold frequency does not have enough photon energy to release electrons from the metal.
3. The threshold frequency of a metal depends mainly on its:
A.
Surface area
B.
Work function
C.
Thickness
D.
Temperature of surrounding air
Correct Answer:
Work function
Explanation:
The threshold frequency is related to the work function by the equation phi = h nu_0, so it depends on the work function of the metal.
4. In the equation phi = h nu_0, the symbol nu_0 represents the:
A.
Frequency of emitted electrons
B.
Frequency of maximum intensity
C.
Threshold frequency
D.
Frequency of reflected light
Correct Answer:
Threshold frequency
Explanation:
In this equation, nu_0 is the minimum frequency required for photoelectric emission, called the threshold frequency.
5. A metal has a threshold frequency of 5 × 10^14 Hz. Which light can cause photoelectric emission from it?
A.
Light of frequency 3 × 10^14 Hz
B.
Light of frequency 4 × 10^14 Hz
C.
Light of frequency 5 × 10^14 Hz
D.
Light of frequency 2 × 10^14 Hz
Correct Answer:
Light of frequency 5 × 10^14 Hz
Explanation:
Photoelectric emission occurs when the incident frequency is equal to or greater than the threshold frequency. Therefore, light of 5 × 10^14 Hz can cause emission.
6. At the threshold frequency, the emitted photoelectrons have:
A.
Maximum kinetic energy
B.
Zero maximum kinetic energy
C.
Very high speed
D.
Infinite kinetic energy
Correct Answer:
Zero maximum kinetic energy
Explanation:
At threshold frequency, the photon energy is just equal to the work function, leaving no energy as kinetic energy for the emitted electron.
7. Which statement about the threshold frequency is correct?
A.
It is the same for all metals
B.
It depends on the intensity of light
C.
It is characteristic of the metal surface
D.
It increases when light intensity increases
Correct Answer:
It is characteristic of the metal surface
Explanation:
Each metal has a particular work function and therefore a characteristic threshold frequency.
8. If the work function of a metal is increased, its threshold frequency will:
A.
Decrease
B.
Increase
C.
Become zero
D.
Remain unrelated to it
Correct Answer:
Increase
Explanation:
Since the threshold frequency is given by nu_0 = phi/h, an increase in work function causes an increase in threshold frequency.
9. A metal has a threshold frequency of 6 × 10^14 Hz. Which radiation cannot produce photoelectric emission?
A.
Radiation of frequency 8 × 10^14 Hz
B.
Radiation of frequency 7 × 10^14 Hz
C.
Radiation of frequency 6 × 10^14 Hz
D.
Radiation of frequency 4 × 10^14 Hz
Correct Answer:
Radiation of frequency 4 × 10^14 Hz
Explanation:
Radiation with frequency below 6 × 10^14 Hz is below the threshold frequency and cannot eject photoelectrons.
10. The threshold frequency is also called the:
A.
Critical frequency
B.
Resonant frequency
C.
Natural frequency
D.
Angular frequency
Correct Answer:
Critical frequency
Explanation:
Threshold frequency is also known as critical frequency because it is the minimum frequency required to start photoelectric emission.
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