Question

A star emits light of 5500 Å wavelength. Its appears blue to an observer on the earth, it means.

• A. Star is going away from the earth
• B. Star is stationary
• C. Star is coming towards earth
• D. None of the above

Answer 1

Answer: (C)

Star is coming towards earth

Answer 2

Blue radiations have the wavelength around 4600$\overset{o}{A}$. It shows that apparent wavelength is smaller than the real wavelength. It means that the star is proceeding towards earth.