Question

The expression for Doppler's shift is given by
$\frac{\Delta v}{v}=\frac{v_{\text {radial }}}{c}$
[Consider the directions from observer to source as positive]
Here, $v_{\text {radial }}$ refers to

• A. the component of the source velocity along the line joining the source to observer
• B. the component of the source velocity along the line joining the observer to the source relative to the observer
• C. the frequency of light as observed by the observer
• D. None of the above

Answer 1

Answer: (B)

In Doppler's shift given by, $\frac{\Delta v}{v}=\frac{v_{\text {radial }}}{c}$ $\frac{\Delta v}{v}=$ fractional change in frequency
$v_{\text {radial }}=$ the component of the source velocity along the lin joining the observer to the source relative to the observer
$c=$ speed of light in vacuum $=3 \times 10^{8} ms ^{-1}$.