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Home » Monochromatic light of wavelength is produced by a helium-neon laser. The power emitted is . How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?
Monochromatic light of wavelength 632.8 \mathrm{~nm} is produced by a helium-neon laser. The power emitted is 9.42 \mathrm{~mW}. How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?
Class 12 | Dual Nature of Radiation and Matter | NCERT | Physics
Monochromatic light of wavelength 632.8 \mathrm{~nm} is produced by a helium-neon laser. The power emitted is 9.42 \mathrm{~mW}. How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?

We are provided that the momentum of the hydrogen atom is equal to the momentum of the photon,

\mathrm{P}=1.047 \times 10^{-27} \mathrm{~kg} \mathrm{~m} / \mathrm{s}

Momentum’s expression is:

P=m v

Where,

v= speed of hydrogen atom

Therefore, v=\frac{p}{m}

=\frac{1.047 \times 10^{-27}}{1.66 \times 10^{-27}}=0.621 \mathrm{~m} / \mathrm{s}

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