Neon gas is generally used in the sign boards. If it emits strongly at 616 nm, calculate (a) the frequency of emission, (b) distance travelled by this radiation in 30 s (c) energy of quantum and (d) number of quanta present if it produces 2 J of energy.


Given:

Wavelength, λ = 616 nm = 616× 10-9m


To find frequency:


Speed of Light = [Frequency] × [Wavelength]


We know speed of light = 3×108 m/s


Frequency, v = [3×108] / [616 × 10-9]


v = 4.87×1014 Hz


To find distance travelled:


Velocity of the radiation = 3× 108 m/s


Therefore, distance travelled in 30s = 30× 3× 108 = 9.0× 109m


To find the energy:


By Planck’s relation we have,


Energy, E = h×v


= [6.626×10-34] × [4.87×1014]


= 3.23×10-19 J


Therefore, the energy of the photon corresponding to light of frequency 4.87×1014 Hz is 3.23×10-19 J.


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