Question

Maximum kinetic energy of photoelectrons depend upon light’s
A. Intensity
B. Frequency
C. Wavelength
D. All of these

Answer 1

Hint: Photo electrons are emitted due to photoelectric effect. Photoelectric effect is a phenomenon in which free electrons are emitted from the surface of metals by absorbing electromagnetic radiation i.e. photons. These emitted electrons are called photo electrons. The answer to this question can be given using Einstein's photoelectric equation.

Formula used:
$K.E. = h\nu - \phi$

Complete answer:
Maximum Kinetic energy of photoelectrons is given by,
$K.E. = h\nu - \phi$
Where, h is the Planck’s constant
            $\nu$ is the frequency of the incident radiation, i.e. light
            $\phi$ is the work function of the metal surface
From the above equation, it can be inferred that the maximum kinetic energy of the photoelectrons depend upon light’s frequency.

So, the correct answer is “Option B”.

Additional Information:
Photo electrons are emitted only when the incident frequency is greater than or equal to the threshold frequency. If the threshold frequency is greater than the incident frequency then the kinetic energy of the light will come out to be negative which is not possible. The value of work function can never be negative.

Note:
When light of suitable frequency $\nu$ falls on a metal target, photo electrons are emitted from the metal having energy ranging from zero to ${K.E}_{max}$. According to the quantum model of light, maximum kinetic energy of photoelectrons depends only on the frequency. According to the classical model of light, kinetic energy depends on the intensity of light. This was later proved false and it was concluded that the kinetic energy of photoelectrons depends only on the frequency of light.