Chapter 2

\(\mathrm{Be}^{3+}\) and a proton are accelerated by the same potential, their de-Broglie wavelengths have the ratio (assume mass of proton = mass of neutron): (a) \(1: 2\) (b) \(1: 4\) (c) \(1: 1\) (d) \(1: 3 \sqrt{3}\)

The mass of an electron is \(m\), charge is \(e\) and it is accelerated from rest through a potential difference of \(V\) volts. The velocity acquired by electron will be : (a) \(\sqrt{\frac{V}{m}}\) (b) \(\sqrt{\frac{e V}{m}}\) (c) \(\sqrt{\frac{2 e V}{m}}\) (d) zero

The spectrum produced from an element is : (a) atomic spectrum (b) line spectrum (c) absorption spectrum (d) any one of the above

Line spectra is characteristic of : (a) molecules (b) atoms (c) radicals (d) none of these

Find the value of wave number \((\bar{v})\) in terms of Rydberg's constant, when transition of electron takes place between two levels of \(\mathrm{He}^{+}\) ion whose sum is 4 and difference is \(2 .\) (a) \(\frac{8 R}{9}\) (b) \(\frac{32 R}{9}\) (c) \(\frac{3 R}{4}\) (d) none of these

A \(\mathrm{H}\) -atom moving at a speed \((v)\) absorbs a photon of \(\lambda=122 \mathrm{~nm}\) and stops. What was the speed of \(\mathrm{H}\) -atom? \(\left(h=6.63 \times 10^{-34} \mathrm{~J}-\mathrm{s}\right)\) (a) \(0.325 \mathrm{~m} / \mathrm{s}\) (b) \(1 \mathrm{~m} / \mathrm{s}\) (c) \(2.5 \mathrm{~m} / \mathrm{s}\) (d) \(3.25 \mathrm{~m} / \mathrm{s}\)

Assume that \(2 \times 10^{-17} \mathrm{~J}\) of light energy is needed by the interior of the human eye to see an object. How many photons of yellow light with \(\lambda=595.2 \mathrm{~nm}\) are needed to generate this minimum energy? (a) 6 (b) 30 (c) 45 (d) 60

The energy of the second Bohr orbit in the hydrogen atom is \(-3.41 \mathrm{eV}\). The energy of the second Bohr orbit of \(\mathrm{He}^{+}\) ion would be : (a) \(-0.85 \mathrm{eV}\) (b) \(-13.64 \mathrm{eV}\) (c) \(-1.70 \mathrm{eV}\) (d) \(-6.82 \mathrm{eV}\)

Which of the following statement(s) is/are consistent with the Bohr theory of the atom (and no others)? (1) An electron can remain in a particular orbit as long as it continuously absorbs radiation of a definite frequency. (2) The lowest energy orbits are those closest to the nucleus. (3) All electrons can jump from the \(K\) shell to the \(M\) shell by emitting radiation of a definite frequency. (a) \(1,2,3\) (b) 2 only (c) 3 only (d) 1,2

Wavelength for high energy EMR transition in H-atom is \(91 \mathrm{~nm}\). What energy is needed for this transition? (a) \(1.36 \mathrm{eV}\) (b) \(1240 \mathrm{eV}\) (c) \(13 \mathrm{eV}\) (d) \(13.6 \mathrm{eV}\)