Chapter 26, Problem 1QAP

To determine

Explain why the existence of a frequency below which photoelectrons are not emitted.

Explanation of Solution

The electromagnetic field is quantized, and it exists in the form of small packets called a photon

Quantized energy of the photon,$E=hf=\frac{hc}{\lambda }$.

Here, h is Plank's constant, f is the frequency of wave, ( is the wavelength of photon and c is the speed of light..

A free moving electron in metal does not eject out of the surface of metal on their own. The minimum amount of energy necessary to take a free electron out of metal is called work function.

Work function,${\varphi }_0=h{f}_o=\frac{hc}{{\lambda }_o}$.

Here, h is Plank's constant, f_o is threshold frequency of the wave, (_o is threshold wavelength of photon and c is the speed of light..

When frequency of falling light is less than threshold frequency, electron will not eject from metal and falling light on the surface can reflect, absorb or transmit.