Question

The energy required to remove an electron from the surface of sodium metal is $3.3eV$. What is the longest wavelength of radiation with which it can show photoelectric effect?
Use $h=6.6\times {10}^{-34}J.s$

• A. $1.75\times {10}^{-7}m$
• B. $3.75\times {10}^{-5}m$
• C. $1.75\times {10}^{-5}m$
• D. $3.75\times {10}^{-7}m$

Answer 1

The correct option is D $3.75\times {10}^{-7}m$

To show photoelectric effect minimum energy needed = $3.3$ eV

So,

$⟹h\nu =3.3eV⟹\frac{hc}{\lambda }=3.3eV⟹\lambda =\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{3.3\times 1.6\times {10}^{-19}}=3.75\times {10}^{-7}m$