Question

The photoelectric threshold for a certain metal surface is $330\stackrel{\circ }{A}$. What is the maximum kinetic energy of photoelectron released, if any, by a radiation of wavelength $1100\stackrel{\circ }{A}$?

• A. $1eV$
• B. $2eV$
• C. $7.5eV$
• D. No electron is emitted

Answer 1

Answer: (D)

No electron is emitted

Wavelength of incident radiation is $\lambda =1100\stackrel{\circ }{A}=1100\times {10}^{-10}m$. Therefore, frequency of incident radiation is

$\nu =\frac{c}{\lambda }=\frac{3\times {10}^8}{1100\times {10}^{-10}}\simeq 0.3\times {10}^{16}Hz$

Threshold wavelength is ${\lambda }_0=330\stackrel{\circ }{A}=330\times {10}^{-10}m$.

Therefore, threshold frequency is

${\nu }_0=\frac{c}{{\lambda }_0}=\frac{3\times {10}^8}{330\times {10}^{-10}}\simeq {10}^{16}Hz$

Since $v<v_0$, no photoelectron is emitted.