Question
What do you mean by gravitational red shift?
Solution
The frequency of light emitted by star decreases and shifts towards red end of the spectrum due to the gravitational field of star.
The decrease in the frequency of light due to gravity is,
where,
g is the acceleration due to gravity due to star at the surface of star,
R is the radius of star, and
c is the velocity of light.
The decrease in the frequency of light due to gravity is,

where,
g is the acceleration due to gravity due to star at the surface of star,
R is the radius of star, and
c is the velocity of light.