$A$ star emits light of $5500 \ \mathring{A}$ wavelength. If it appears blue to an observer on the Earth,it means:

$A$ star is moving towards the earth with a speed of $4.5 \times 10^6 \ m/s$. If the true wavelength of a certain line in the spectrum received from the star is $5890 \ \mathring A$,its apparent wavelength will be about........$\mathring A$ $[c = 3 \times 10^8 \ m/s]$

For an observer on the earth, if a spectral line of wavelength $6600 \, \text{Å}$ emitted by a star is found to be red shifted by $22 \, \text{Å}$, then the star is

Write the formula for the Doppler shift for light.

$A$ rocket is moving away from the Earth at a speed of $0.2c$,where $c$ is the speed of light. It emits a signal of frequency $4 \times 10^7 \text{ Hz}$. What will be the frequency observed by an observer on the Earth?

$A$ star producing light of wavelength $6000 \ \mathring{A}$ moves away from the Earth with a speed of $5 \ km/s$. Due to the Doppler effect, the shift in wavelength will be $...... \ \mathring{A}$ $(c = 3 \times 10^8 \ m/s)$.