Modern Physics 1 Question 26
23. In hydrogen spectrum, the wavelength of line is ; whereas in the spectrum of a distant galaxy line wavelength is . Estimated speed of galaxy with respect to earth is
(a)
(b)
(c)
(d)
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Solution:
- Since, the wavelength
is increasing, we can say that the galaxy is receding. Doppler effect can be given by
If we take the approximation then Eq. (i) can be written as
From here
which is almost equal to the previous answer. So, we may use Eq. (ii) also.