Question

Work function of nickel is 5.01 eV. When ultraviolet radiation of wavelength 2000 $\mathring{A}$ is incident on electrons are emitted. What will be the maximum velocity of emitted electrons?

• A. $3\times 10^{8}m{s}^{-1}$
• B. $6.46\times 10^{5}m{s}^{-1}$
• C. $10.36\times 10^{5}m{s}^{-1}$
• D. $8.54\times 10^{6}m{s}^{-1}$

Answer 1

Answer: (B)

Energy corresponding to 2000 $\mathring{A}$
E = $\frac{12375}{\lambda }=\frac{12375}{2000}eV=6.2eV$
Maximum kinetic energy
K = hv $-h{v}_0$
K = E - W
= $(6.2-5.01)eV=1.19eV$
Now $\frac{1}{2}\times 9.1\times 10^{-31}\times V_{max}^2=1.19\times 1.6\times 10^{-19}$
or $v_{max}^2=\frac{1.19\times 1.6\times 10^{-19}\times 2}{9.1\times 10^{-31}}$
or $v_{max}^2=0.418\times 10^{12}=4.18\times 10^{10}$
or $v_{max}=6.46\times 10^{5}m/s$