Question

In a photoelectric effect, electrons are emitted

• A. With a maximum velocity proportional to the frequency of the incident radiation
• B. At a rate that is independent of the intensity of the incident radiation
• C. Only if the frequency of the incident radiation is above a certain threshold value
• D. Only if the temperature of the emitter is high

Answer 1

The correct option is C Only if the frequency of the incident radiation is above a certain threshold value

The Einstein's equation for photoelectric effect is given by, $K{E}_{max}=hf-h{f}_0$ where $K{E}_{max}=$ maximum kinetic energy of photo electron, $f=$ frequency of incident light and $f_0=$ threshold frequency.

Since maximum kinetic energy of photo electrons is greater than zero so

$hf-h{f}_0>0$ or $f>f_0$