A star, which is emitting radiation at a wavelength of 5000 A, is approaching the earth with a velocity of 1.5×10⁶ m/s. The change in wavelength of the radiation as received on the earth is

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(1) 25 A. Given: λ=5000 A, star approaching at v=1.5×10⁶ m/s, c=3×10⁸ m/s. Idea: for v c the Doppler shift in wavelength is simply (Δλ)/λ=v/c. v/c=(1.5×10⁶)/(3×10⁸)=5×10⁻³. Δλ=λ×v/c=5000×5×10⁻³. Δλ=25 A. (The star approaches, so the light is blue-shifted: the received wavelength is 4975 A.)

A star, which is emitting radiation at a wavelength of 5000 A, is approaching the earth with a velocity of 1.5×10⁶ m/s. The change in wavelength of the radiation as received on the earth is

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