Atoms

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

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

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

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

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

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

The de-Broglie wavelength of an electron moving with a velocity c/2 (c = velocity of light in vacuum) is equal to the wavelength of a photon. The ratio of the kinetic energies of electron and photon is

• 1 : 4

• 1 : 2

• 1 : 1

• 2 : 1

Ratio of longest wavelengths corresponding to Lyman and Balmer series in hydrogen spectrum is

• $\frac{5}{27}$

• $\frac{3}{23}$

• $\frac{7}{29}$

• $\frac{9}{31}$

The ionization energy of hydrogen is 13.6 eV. The energy of the photon released when an electron jumps from the first excited state (n = 2) to the ground state of a hydrogen atom is

• 3.4 eV

• 4.53 eV

• 10.2 eV

• 13.6 eV