Question

The work function of a substance is `4.0 eV`. The longest wavelength of light that can cause photo electron emission from this substance is approximately. (a) `540 nm` (b ) `400nm` (c ) `310 nm` (d) `220 nm`
A. `540 nm`
B. `400 nm`
C. `310 nm`
D. `220 nm`

Answer 1

Correct Answer - C
`lambda_(0) = (hc)/(W_(0)) = (12400)/(4) = 3100 Å = 310 nm`