Question

When blue light is incident on metal surface, photoelectrons are emitted. When green light is incident, no photoelectrons are emitted. What is the number of photoelectrons emitted when yellow light is incident?

• A. Zero
• B. Equal to the number for blue light
• C. Less than for blue light
• D. Greater than for blue light

Hint:

The emission of photoelectrons depends on the frequency of the incident light and the work function of the metal. The intensity or number of photoelectrons depends on the number of photons hitting the surface.

Answer 1

The Correct Option is B

Photoelectron emission occurs when light of sufficient energy (frequency) strikes a metal surface, as per the photoelectric effect. The energy of a photon is given by \( E = h \nu \), where \( h \) is Planck's constant and \( \nu \) is the frequency of the incident light. For the photoelectric effect to occur, the frequency of the light must exceed a certain threshold frequency \( \nu_0 \), which corresponds to the work function of the metal. - Blue light has a higher frequency than green and yellow light, and since it causes the emission of photoelectrons, it implies the energy of blue light is above the threshold. - Green light has a lower frequency than blue light, and since it does not emit photoelectrons, it implies the energy of green light is below the threshold for this particular metal. - Yellow light has a frequency slightly lower than blue but still might be above the threshold. If yellow light has the same or greater energy than the threshold, photoelectrons will be emitted in equal or lesser quantity as for blue light. Thus, the number of photoelectrons emitted with yellow light will be equal to that emitted by blue light, assuming the energy of yellow light is sufficient to release photoelectrons.