Question

A beam of light is strikes on a piece of metal whose work function is 6.0 eV. Calculate the maximum kinetic energy of photoelectrons ejected from the metals surface if frequency of light is $7.2\times {10}^{15}Hz$.

• A. 7 eV
• B. 13 eV
• C. 19 eV
• D. 24 eV
• E. No photoelectrons will be produced

Answer 1

Answer: (D)

24 eV

Given : $\nu =7.2\times {10}^{15}$ Hz $\varphi =6.0$ eV

Planck's constant $h=\frac{6.63\times {10}^{-34}}{1.6\times {10}^{-19}}=4.14\times {10}^{-15}$ eV s

Maximum kinetic energy of photoelectrons $K.E_{max}=h\nu -\varphi$

$\therefore$ $K.E_{max}=(4.14\times {10}^{-15})\times (7.2\times {10}^{15})-6.0=30-6=24$ eV