Page 7 - AAS & AES & FES 01082016_Neat

Numerical 1
Calculate the observed frequency of the radiation emitted from a sodium atom in a vacuum
5
if the atom is moving toward the detector at a velocity of 8.00×10 m/s and if the
wavelength of radiation emitted by Sodium with no motion is 588.995 nm.

Ans:
8
Velocity of light in vacuum = c = 2.997925×10 m/s
5
Velocity of Sodium atom = v = 8.00×10 m/s
Wavelength of radiation = λ = 588.995 nm
f =c/λ [frequency = velocity of light/ wavelength]

Atom is moving toward detector so speed of atom will increased by c + v

8
Total velocity = 2.997925×10 + 8.00×10 5

= 300592500 m/s
Observed frequency = total velocity of light/ wavelength

= 300592500 / 588.995 × 10 -9
14
= 5.10348 × 10 Hz

Numerical 2

Calculate the observed frequency of the radiation emitted from a sodium atom in a vacuum
5
if the atom is moving away from the detector at a velocity of 8.00×10 m/s and if the
wavelength of radiation emitted by Sodium with no motion is 588.995 nm.

Ans:
8
Velocity of light in vacuum = c = 2.997925×10 m/s
5
Velocity of Sodium atom = v = 8.00×10 m/s
Wavelength of radiation = λ = 588.995 nm

f =c/λ [frequency = velocity of light/ wavelength]

Atom is moving away from detector so speed of atom will decreased by c - v

8

Total velocity = 2.997925×10 - 8.00×10 5

= 298992500 m/s

Observed frequency = total velocity of light/ wavelength

= 298992500 / 588.995 × 10 -9

14
= 5.07632× 10 Hz

6