Question

When the wavelength of light coming from a distant star is measured it is found shifted towards red. Then the conclusion is(a) The star is approaching the observer(b) The star recedes away from earth(c) There is gravitational effect on the light(d) The star remains stationary

Answer 1

Redshift and blueshift describe how light shifts toward shorter or longer wavelengths as objects in space (such as stars or galaxies) move closer or farther away from us. The concept is key to charting the universe's expansion.

Visible light is a spectrum of colors, which is clear to anyone who has looked at a rainbow. When an object moves away from us, the light is shifted to the red end of the spectrum, as its wavelengths get longer. If an object moves closer, the light moves to the blue end of the spectrum, as its wavelengths get shorter.