question_answer

The work function of a substance is\[4.0\text{ }eV\]. The longest wavelength of light that can cause photoelectron emission from this substance is approximately                        [AIEEE 2004]

A) 540 nm

B) 400 nm

C) 310nm

D) 220 nm

Correct Answer: C

Solution :

[c] The work function is given by

where,is the threshold wavelength,