A star, which is emitting radiation at a wavelength of 5000

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A star, which is emitting radiation at a wavelength of 5000 Å, is approaching the earth with a velocity of 1.50 × 10⁶ m/s. The change in wavelength of the radiation as received on the earth is

Given : Wavelength (λ) = 5000 Å
velocity of star (v) = 1.5 × 10⁶ m/s.
We know that wavelength of the approaching star (λ')

(λ') = λ	c - v
	c

or,	λ'	=	c - v	= 1 -	v
	λ		c		c

or,	v	= 1 -	λ'	=	λ - λ'	=	Δλ
	c		λ		λ		λ

Therefore,

Δλ = λ ×	v	= 5000 ×	1.5 × 10⁶	= 25 Å
	c		3 × 10 × 10⁸

[where ∆λ = Change in the wavelength]