The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately equal to

Options

A. 540 nm
B. 400 nm
C. 310 nm
D. 220 nm

Answer

C

Explanation

Work function , `phi_(0) = (hc)/(lamda_("longest")`
or `lamda_("longest")=(hc)/(phi_0)=((6.63 x10^(-34))xx(3xx10^8))/(4.0 xx1.6 xx10^(-19))`
`~~310 xx10^(-9) m = 310 nm `