Chapter 2

What is the energy content per photon \((J)\) for light of frequency \(4.2 \times 10^{14}\) ? (a) \(2.8 \times 10^{-21}\) (b) \(2.5 \times 10^{-19}\) (c) \(2.8 \times 10^{-19}\) (d) \(2.5 \times 10^{-18}\)

The momentum (in \(\mathrm{kg}-\mathrm{m} / \mathrm{s}\) ) of photon having \(6 \mathrm{MeV}\) energy is : (a) \(3.2 \times 10^{-21}\) (b), \(2.0\) (c) \(1.6 \times 10^{-21}\) (d) none of these

The H-spectrum show: (a) Heisenberg's uncertainty principle (b) Diffraction (c) Polarization (d) Presence of quantized energy level

The energy of an electron moving in \(n^{\text {th }}\) Bohr's orbit of an element is given by \(E_{n}=\frac{-13.6}{n^{2}} Z^{2}\) \(\mathrm{eV} /\) atom \((Z=\) atomic number \()\). The graph of \(E\) vs. \(Z^{2}\) (keeping "n" constant) will be :

If \(\varepsilon_{0}\) be the permittivity of vacuum and \(r\) be the radius of orbit of \(\mathrm{H}\) -atom in which electron is revolving then velocity of electron is given by : (a) \(v=\frac{e}{\sqrt{4 \pi \varepsilon_{0} r m}}\) (b) \(v=e \times \sqrt{4 \pi \varepsilon_{0} r m}\) (c) \(v=\frac{4 \pi \varepsilon_{0} r m}{e}\) (d) \(v=\frac{4 \pi \varepsilon_{0} r m}{e^{2}}\)

Splitting of spectral lines under the influence of magnetic field is called (a) Zeeman effect (b) Stark effect (c) Photoelectric effect (d) None of these

The photoelectric emission from a surface starts only when the light incident upon the surface has certain minimum : (a) intensity (b) wavelength (c) frequency (d) velocity

If \(\lambda_{0}\) and \(\lambda\) be the threshold wavelength and the wavelength of incident light, the velocity of photo-electrons ejected from the metal surface is : (a) \(\sqrt{\frac{2 h}{m}\left(\lambda_{0}-\lambda\right)}\) (b) \(\sqrt{\frac{2 h c}{m}\left(\lambda_{0}-\lambda\right)}\) (c) \(\sqrt{\frac{2 h c}{m}\left(\frac{\lambda_{0}-\lambda}{\lambda \lambda_{0}}\right)}\) (d) \(\sqrt{\frac{2 h}{m}\left(\frac{1}{\lambda_{0}}-\frac{1}{\lambda}\right)}\)

A light source of wavelength \(\lambda\) illuminates a metal and ejects photo- electrons with \(\left(\mathrm{K} . \mathrm{E}_{t}\right)_{\max }=1 \mathrm{eV}\) Another light source of wavelength \(\frac{\lambda}{3}\), ejects photo-electrons from same metal with (K. E.) \(_{\max }=4 \mathrm{eV}\) Find the value of work function? (a) \(1 \mathrm{eV}\) (b) \(2 \mathrm{eV}\) (c) \(0.5 \mathrm{eV}\) (d) None of these

Electromagnetic radiation having \(\lambda=310 \AA\) is subjected to a metal sheet having work function \(=12.8 \mathrm{eV}\). What will be the velocity of photo-electrons having maximum kinetic energy. (a) 0, no emission will occur (b) \(4.352 \times 10^{6} \mathrm{~m} / \mathrm{s}\) (c) \(3.09 \times 10^{6} \mathrm{~m} / \mathrm{s}\) (d) \(8.72 \times 10^{6} \mathrm{~m} / \mathrm{s}\)