In Bohr's model of hydrogen atom, the electron circulates around the nucleus in a path of radius 5 x 10^-11 m at a frequency of 6.8 x 10¹⁵ Hz. The value of magnetic field and equivalent magnetic moment will be

• 15.4 T and 8.9 x 10^-24 A-m²

• 13.4 T and 8.9 x 10^-24 A-m²

• 18.4 T and 9.8 x 10^-24 A-m²

• 13.4 T and 9.8 x 10^-24 A-m²

Which element has K_{$\mathrm{\alpha }$} line of wavelength in 1.785 $\stackrel{°}{\mathrm{A}}$ ?

• Copper

• Cobalt

• Sodium

• Aluminium

The energy levels of a certain atom are represented in the figure given below. During the transition from 2E to E level, a photon of wavelength is emitted. The wavelength of photon produced during transition from 4 / 3E level to E will be

• $3\mathrm{\lambda }$

• $\frac{\mathrm{\lambda }}{3}$

• $\frac{3\mathrm{\lambda }}{3}$

• $\frac{4\mathrm{\lambda }}{3}$

J.J. Thomson's cathode ray tube experiment demonstrated that

• cathode rays are streams of negatively charged ions

• all the mass of an atom is essentially in the nucleus

• the e/m of electrons is much greater than the e/m of protons

• the e/m ratio of the cathode ray particles changes when a different gas is placed in the discharge tube

175.

Wavelength of light emitted from second orbit to first orbit in a hydrogen atom is

• 6563 $\stackrel{\circ }{\mathrm{A}}$

• 4102 $\stackrel{\circ }{\mathrm{A}}$

• 4861 $\stackrel{\circ }{\mathrm{A}}$

• 1215 $\stackrel{\circ }{\mathrm{A}}$

Band spectrum is also called

• molecular spectrum

• atomic spectrum

• flash spectrum

• line absorption spectrum

The ionization potential of hydrogen is 13.6 V. The energy required to remove an electron from the second orbit of hydrogen is

• 3.4 eV

• 6.8 eV

• 13.6 eV

• 1.51 eV

The ratio of the de-Broglie wavelength of an $\mathrm{\alpha }$-particle and a proton of same kinetic energy is

• 1 : 2

• 1 : 1

• 1 : $\sqrt{2}$

• 4 : 1

The ionisation potential of hydrogen atom is -13.6 eV. An electron in the ground state of a hydrogen atoms absorbs a photon of energy 12.75 eV. How many different spectral line can one expect when the electron make a downward transition ?

• 1

• 4

• 2

• 6

If the electron in a hydrogen atom jumps from an orbit with level n₁ = 2 to an orbit with level n₂ = 1 the emitted radiation has a wavelength given by

• $\mathrm{\lambda } = \frac{5}{3\mathrm{R}}$

• $\mathrm{\lambda } = \frac{4}{3\mathrm{R}}$

• $\mathrm{\lambda } = \frac{\mathrm{R}}{4}$

• $\mathrm{\lambda } = \frac{3\mathrm{R}}{4}$