Question

Threshold frequency for a metal is 10¹⁵ Hz. Light of `lambda` = 4000 Å falls on its surface. Which of the following statements is correct?

Options

• No photoelectric emission takes place.

• Photoelectrons come out with zero speed.

• Photoelectrons come out with 10³ m/s speed.

• Photoelectrons come out with 10⁵ m/s speed.

Answer 1

No photoelectric emission takes place.

Explanation:

Frequency of light of wavelength

`(lambda = 4000  Å)  "is v" = "c"/lambda = (3 xx 10^8)/(4000 xx 10^-10) = 0.75 xx 10^15`

which is less than the set frequency threshold As a result, no photoelectric emission occurs.