Question

The photoelectrons emitted from the surface of sodium metal are
A. Of speeds from zero to a certain maximum
B. Of same De-Broglie wavelength
C. Of same kinetic energy
D. Of same frequency

Answer 1

Hint: Before going to solve this question let us understand about photocells. It converts light energy into electrical energy. This photocell works on the principle of the photoelectric effect.

Formula Used:
The formula to find the maximum kinetic energy of the photon is,
\[K.{E_{\max }} = E - W\]
Where, E is energy of the photon and W is work function.

Complete step by step solution:
If the electron emits from the surface of the metal, then the maximum kinetic energy of an electron is,
\[K.{E_{\max }} = E - W\]
When a photon is an incident on a metal surface, the electron in the metal absorbs and gets excited with the maximum speed. Suppose when the energy incident on the metal surface starts colliding with the electrons which are present in the metal then, the speed of an electron will be less than the maximum speed says, \[v < {v_{\max }}\].

After several collisions, the range of the speed may vary from zero to maximum value depending on the incident photon energy. According to the other options, if the energy of the electron is different then, it has a different wavelength, kinetic energy, and also has a different frequency.

Therefore, the photoelectrons that are emitted from the surface of the metal surface are of speeds that range from zero to a certain maximum value depending upon the energy of the incident photon.

Hence, option A is the correct answer.

Additional informationThere are three types of Photoelectric cells, they are photo-emissive cell, photovoltaic cell, and photo-conductive cell. Examples of photoelectric devices are Light-emitting diodes (LED), phototransistors, solar cells, etc.

Note:Here, in this question it is important to remember how photocells work and how the photoelectric effect takes place, and what are the driving conditions for it to happen.