Question

Photons of frequency $3.2 \times 10^{16} Hz$ is used to irradiate a metal surface, the maximum kinetic energy of the emitted photo-electron is $\frac{3^{ th }}{4}$. of the energy of the irradiating photon? What is the threshold frequency of the metal?

• A. $2.4 \times 10^{25} Hz$
• B. $2.4 \times 10^{16} Hz$
• C. $1.6 \times 10^{15} Hz$
• D. $8 \times 10^{15} Hz$

Answer 1

Answer: (D)

Apply, $h v-h v_{0}=k E$

Apply, $ h v-h v_{0}=\frac{3}{4} h v$

$\Rightarrow h v-\frac{3}{4} h v=h v_{0}$

$\frac{h v}{4}=h v_{0}$

$\Rightarrow \frac{v}{4}=v_{0}$

$\frac{3.2 \times 10^{16}}{4}=v_{0}$

$=8 \times 10^{15} Hz$