Question

Photoelectric emission occurs only when the incident light has more than a certain minimum

• A. Power
• B. Wavelength
• C. Intensity
• D. Frequency

Answer 1

Answer: (D)

According to Einstein's photoelectric equation
${\text{K}}_{\text{max}}=\text{h}\upsilon -\text{h}{\upsilon }_0$
Since $K_{max}$ is positive, the photoelectric emission occurs only if
$\text{h}\upsilon >\text{h}{\upsilon }_0\text{or}\upsilon >{\upsilon }_0$
The photoelectric emission occurs only when the incident light has more than a certain minimum frequency. The minimum frequency is called threshold frequency.