CBSE Class 12 Physics 2022 Term 2 Delhi Set 1 Solved Paper

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Question : 9 of 12
 
Marks: +1, -0
(a) Calculate the energy and momentum of a photon in a monochromatic beam of wavelength 331.5nm.3
(b) How fast should a hydrogen atom travel in order to have the same momentum as that of the photon in part (a)?
Solution:
(a) Energy =E=hcλ
Or, E=6.6×10−34×3×108331.5×10−9
∴E=6×10−19J
Momentum =p=hλ
Or, p=6.6×10−34331.5×10−9
∴p=2×10−27kg.m∕s
(b) Momentum of Hydrogen atom
=p=2×10−27kg.m∕s
p=mv
Or, v=pm
Or, v=2×1027kg.m∕s1a.m.u.
Or, v=2×10−27kg.m∕s1.66×10−27kg
∴v=1.2m∕s
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