As an electron makes a transition from an excited state to the ground state of a hydrogen – like atom/ion:

• kinetic energy, potential energy and total energy decrease

• kinetic energy decreases, potential energy increases but total energy remains same

• kinetic energy and total energy decrease but potential energy increases

• its kinetic energy increases but the potential energy and total energy decrease

Energy required for the electron excitation in Li⁺⁺ from the first to the third Bohr orbit is

• 36.3 eV

• 108.8 eV

• 122.4 eV

• 12.1 eV

B.

108.8 eV

Hydrogen (₁H¹), deuterium (₁H²), singly ionised helium (₂He⁴⁺) and doubly ionised lithium (₃Li⁸)²⁺ all have one electron around the nucleus. Consider an electron transition from n =2 to n=1. If the wavelengths of emitted radiation are λ₁,λ₂,λ₃ andλ₄, respectively for four elements, then approximately which one of the following is correct?

•  4λ₁=2λ₂=2λ₃ =λ₄

•  λ₁=2λ₂=2λ₃ =λ₄

•  λ₁=λ₂=4λ₃ =9λ₄

•  λ₁=2λ₂=3λ₃ =4λ₄

If a source of power 4kW produces 10²⁰ photons/second, the radiation belongs to a part of the spectrum called

• X -rays

• ultraviolet rays

• microwaves

• γ rays

In a hydrogen like atom, electron makes the transition from an energy level with quantum number n to another with a quantum number (n – 1). If n >> 1, the frequency of radiation emitted is proportional to 

• 1/n

• 1/n²

• 1/n^3/2

• 1/n³