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Atoms

Multiple Choice Questions

51.

The principle of LASER action involves

amplification of particular frequency emitted by the system
population inversion
stimulated emission
All ofthe above

52.

Solar spectrum is an example for

line emission spectrum
continuous emission spectrum
band absorption spectrum
line absorption spectrum

53.

The ratio of minimum wavelengths of Lyman and Balmer series will be

1.25
0.25
5
10

54.

Hydrogen atom does not emit X-rays because

it contains only a single electron
energy levels in it are far apart
its size is very small
energy levels in it are very close to each other

55.

In the Bohr model of hydrogen atom, the electron is pictured to rotate in a circular orbit of radius 5 x 10^-11 m at a speed 2.2 × 10⁶ m/s. What is the current associated with electron motion ?

1.12 mA
3 mA
0.75 mA
2.25 mA

56.

If an electron and a proton have the same de-Broglie wavelength, then the kinetic energy of the electron is

zero
less than that of a proton
more than that of a proton
equal to that of a proton

57.
In ruby laser, the stimulated emission is due to transition from

metastable state to any lower state

any higher state to lower state

metastable state to ground state

any higher state to ground state

metastable state to ground state

For a ruby laser, a crystal of ruby is formed into a cylinder. A fully reflecting mirror is placed on one end and a partially reflecting mirror on the other. A high-intensity lamp is spiraled around the ruby cylinder to provide a flash of white light that triggers the laser action. The green and blue wavelengths in the flash excite electrons in the chromium atoms to a higher energy level. Upon returning to their normal state, the electrons emit their characteristic ruby-red light. The mirrors reflect some of this light back and forth inside the ruby crystal, stimulating other excited chromium atoms to produce more red lght, until the light pulse builds up to high power and drains the energy stored in the crystal. In ruby laser stimulated emission is due to transition from metastable state to ground state.