Question

The work functions for metals $A, B$ and $C$ are respectively $1.92\, eV,\, 2.0\, eV$ and $5\, eV$. According to Einstein's equation, the metal(s) which will emit photoelectrons for a radiation of wavelength $4100\,?$ is/are

• A. A only
• B. A and B
• C. All of these
• D. None of these

Answer 1

Answer: (B)

A and B

Answer 2

Work function for wavelength of $4100\, ?$ is $W =\frac{h c}{\lambda}$ $=\frac{6.62 \times 10^{-34} \times 3 \times 10^{8}}{4100 \times 10^{-10}}$ $=4.8 \times 10^{-19} J$ $=\frac{4.8 \times 10^{-19}}{1.6 \times 10^{-19}} eV =3\, eV$ Now, we have $W_{A}=1.92\, eV,\, W_{B}=2.0\, eV,\, W_{C}=5 \,eV$ Since, $W_{A} < W$ and $W_{B} < W$, hence, $A$ and $B$ will emit photoelectrons.