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Class 12
Physics
Wave Optics
the 6563 aring h2 line emitted by hydrogen in a...

Question:
The 6563 Å H₂ line emitted by hydrogen in a star is found to be red shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.

Answer:

Given that,

Wavelength of H₂ line emitted by hydrogen, λ = 6563 Å = 6563 × 10^-10 m.

Star’s red-shift can be obtain by, (λ' - λ) = 15 Å = 15 x 10^-10 m

We know that, Speed of light, c = 3 x 10⁸ m/s

Let the velocity of the star receding away from the Earth be v. Since the star is receding away, hence its velocity v is negative.

The red shift is related with velocity as: λ' - λ = v/c λ

∴ v = c/λ x (λ' - λ) = 3 x 10⁸ x 15 x 10^-10 / 6563 x 10^-10 = 6.87 x 10⁵ m/s

Therefore, the speed with which the star is receding away from the Earth is -6.87 × 10⁵ m/s.

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Question:
The 6563 Å H₂ line emitted by hydrogen in a star is found to be red shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.

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Question: The 6563 Å H2 line emitted by hydrogen in a star is found to be red shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.

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Question:
The 6563 Å H₂ line emitted by hydrogen in a star is found to be red shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.