JEE PYQ: Waves And Sound Question 3
Question 3 - 2021 (18 Mar Shift 2)
A galaxy is moving away from the earth at a speed of 286 kms$^{-1}$. The shift in the wavelength of a red line at 630 nm is $x \times 10^{-10}$ m. The value of $x$, to the nearest integer, is __________. [Take the value of speed of light $c$, as $3 \times 10^8$ ms$^{-1}$]
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Answer: 6
Solution
$\frac{\Delta\lambda}{\lambda} \cdot c = v$
$\Delta\lambda = \frac{v}{c} \times \lambda = \frac{286}{3 \times 10^5} \times 630 \times 10^{-9} = 6 \times 10^{-10}$
BETA
