Question

Write Einsten's photoelectric equation. State clearly how this equation is obtained using the photon picture of electromagnetic radiation. Write the three salient features observed in photoelectric effect which can be explained using this equation

Answer 1

Solution:-

Einstein's photoelectric equation is,

$K_{max}=h\upsilon -{\varphi }_o$

Where,

$K_{max}$=Maximum kinetic energy of a photo electron.

$h\upsilon$ =Energy of a quantum or a photon of incident light.

${\varphi }_o$=Work function of photoelectric surface.

Since,

$K_{max}$depends on energy of a Photon. It shows that Photoelectric effect arises from the absorption of a single quantum of electromagnetic radiation or a single Photon.

salient features:-

1) $K_{max}$ according to the Einstein's equation is independent of intensity of radiation. This\quad is verified experimentally correct.

2) Also$K_{max}$ is dependent inversely on work function of the surface. And if incident light has energy less than the birth function, no photo electrons are emitted, no matter what the intensity of the light is.

3) Intensity of photo electrons increases when intensity of light increases only if the frequency of light is greater than the threshold frequency.