Q. In the photoelectric effect, if the frequency of incident light is doubled, what happens to the kinetic energy of the emitted electrons?
A.It doubles
B.It quadruples
C.It remains the same
D.It becomes zero
Solution
The kinetic energy of the emitted electrons is given by KE = hf - φ. If the frequency is doubled, the kinetic energy increases by a factor of four, since KE is proportional to the frequency.
Q. In the photoelectric effect, the kinetic energy of the emitted electrons depends on which of the following?
A.Frequency of the incident light
B.Intensity of the incident light
C.Wavelength of the incident light
D.All of the above
Solution
The kinetic energy of the emitted electrons in the photoelectric effect depends on the frequency of the incident light, as per Einstein's photoelectric equation.
Correct Answer: A — Frequency of the incident light
Q. In the photoelectric effect, what happens to the emitted electrons if the frequency of the incident light is just at the threshold frequency?
A.They are emitted with maximum kinetic energy
B.They are emitted with zero kinetic energy
C.They are not emitted
D.They are emitted with negative kinetic energy
Solution
At the threshold frequency, the energy of the incident photons is equal to the work function, resulting in emitted electrons having zero kinetic energy.
Correct Answer: B — They are emitted with zero kinetic energy
Q. In the photoelectric effect, what happens to the kinetic energy of emitted electrons if the intensity of light is increased while keeping frequency constant?
A.Increases
B.Decreases
C.Remains the same
D.Becomes zero
Solution
The kinetic energy of emitted electrons remains the same as it depends on the frequency, not intensity.
Q. In the photoelectric effect, what happens to the kinetic energy of the emitted electrons if the frequency of the incident light is increased?
A.It decreases
B.It remains constant
C.It increases
D.It becomes negative
Solution
The kinetic energy of the emitted electrons increases with the frequency of the incident light, as given by the equation KE = hf - φ, where φ is the work function.
Q. In the photoelectric effect, what is the effect of increasing the wavelength of incident light?
A.Increases the kinetic energy of emitted electrons
B.Decreases the kinetic energy of emitted electrons
C.Has no effect on the photoelectric effect
D.Increases the number of emitted electrons
Solution
Increasing the wavelength decreases the frequency of the light, which reduces the energy of the incident photons, thus decreasing the kinetic energy of emitted electrons.
Correct Answer: B — Decreases the kinetic energy of emitted electrons
Q. In the photoelectric effect, which of the following factors does NOT affect the photoelectric current?
A.Intensity of light
B.Frequency of light
C.Surface area of the metal
D.Type of metal
Solution
The frequency of light must be above a certain threshold to emit electrons, but once that is achieved, the photoelectric current depends on the intensity, not the frequency.
