Practicing Success

Target Exam

CUET

Subject

Physics

Chapter

Dual Nature of Radiation and Matter

Question:

A specific metal's work function is 4.2 eV. Will this metal emit photoelectrically for incident light with a 330 nm wavelength? Also mark the correct reason for the answer.

Options:

Yes, because \(\nu \)>\(\nu \)0

No, because \(\nu \)<\(\nu \)0

Yes, because \(\nu \)<\(\nu \)0

No, because \(\nu \)>\(\nu \)0

Correct Answer:

No, because \(\nu \)<\(\nu \)0

Explanation:

The minimum threshold frequency is given by

 \(\nu \)0 = \(\phi\)0/h

metal's work function \(\phi\)0 = 4.2 eV

h = 6.6×10-34 Js

So, \(\nu \)= 4.2×1.6×10-19/6.6×10-34

\(\nu \)= 1.018×1015 Hz                        ...............................(1)

the relation between frequency and wavelength is given by 

\(\nu \) = c/\(\lambda \)

            = 3 × 108/330 × 10-9

            =0.9 ×1015 Hz                            .................................(2)

So from ...(1) and ...(2) it is clear that \(\nu \)<\(\nu \)0, so this metal will NOT emit photoelectrically.