The following figure represents a wave front $AB$ which passes from air to another transparent medium and produces a new wave front $CD$ after refraction. The refractive index of the medium is ($PQ$ is the boundary between air and the medium).

When a source of light is receding away from an observer, then the spectral lines will get displaced towards

The sun is rotating about its own axis. The spectral lines emitted from the two ends of its equator, for an observer on the earth will show

The observed wavelength of light coming from a distant galaxy is found to be increased by $0.5 \%$ as compared with that coming from a terrestrial source. The galaxy is,

A star producing light of wavelength $6000 \stackrel{\circ }{\mathrm{A}}$ moves away from the earth with a speed of $5 \mathrm{km} {\mathrm{s}}^{-1}$. Due to Doppler effect, the shift in wavelength will be, $c=3\times {10}^8 \mathrm{m} {\mathrm{s}}^{-1}$,

A rocket is moving away from the earth at a speed of $6\times {10}^7 \mathrm{m} {\mathrm{s}}^{-1}$. The rocket has blue light in it. What will be the wavelength of light recorded by an observer on the earth? (Wavelength of blue light$=4600 \mathrm{\AA }$.)

A spectral line $\lambda=5000$ $\AA$ in the light coming from a distant star is observed as $5200 \mathrm{\AA }$. What will be recession velocity of the star?