IGNOU BPHET 141 2026 - A star emits light of wavelength and recedes from Earth at

Question

A star emits light of wavelength $500\text{ nm}$ and recedes from Earth at speed 0.50c. Calculate the observed wavelength.

19 Jan 2026

Answer :

Word Count : 114

The observed wavelength of light from a receding source is given by the relativistic Doppler formula: [ \lambda_{\text{obs}} = \lambda_{\text{em}} \sqrt{\frac{1 + \beta}{1 - \beta}} ] where (\beta = \frac{v}{c}), (v) is the speed

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