Question

Which of the following statement(s) is/are correct regarding photoelectric effect?

• A. No electrons are ejected, regarding of the intesity of the radiation, unless the frequency exceeds a threshold value characteristic of the metal
• B. The kinetic energy of the ejected electrons increases linearly with the frequency of incident radiation but is independent of the intensity of the radiation
• C. Even at low intensities, electrons are ejected immediately if the wavelength is above threshold value
• D. It is a directed evidence for the dual nature of light

Answer 1

Answer: (A), (B)

The kinetic energy of the ejected electrons increases linearly with the frequency of incident radiation but is independent of the intensity of the radiation

$K{E}_{max}$ of photoelectrons ejected depends only on frequency and not on its intensity.
We know that $K{E}_{max}=h\nu -h{\nu }_0$
where, $\nu =$ frequency of incident light
${\nu }_0=$ threshold frequency
From the above equation, it is observed that the kinetic energy increases linearly with the frequency of incident radiation but is independent of the intensity of radiation.
The wavelength is inversely propertional to energy. If the wavelength is more than the threshold value, then the energy of the incident radiation is lower than threshold energy. So, electrons can not be ejected.
Also, photoelectric effect is a direct evidence for the particle nature of light not of dual nature. Hence option a and b are correct.