Only when the incoming light has more than a certain minimum does photoelectric emission take place.
Power
Wavelength
Intensity
Frequency
Option A) Power is a rate at which work is done. Power is also the rate at which energy is expended.
Option B) The wavelength is defined as the distance between any two consecutive identical points to the waveform.
Option C) Intensity is a quantity of energy the wave conveys per unit time across a surface of unit area.it is generally measured with units of watts per square meter.
Option D) Photoelectric emission occurs only when the incident light has more than a certain minimum frequency. This minimum frequency is called Threshold frequency.
Therefore, the correct answer is D) Frequency