A star of mass M and radius R is made up of gases. The average gravitational pressure compressing the star due to gravitational pull of the gases making up the star depends on R as

A (non-rotating) star collapses onto itself from an initial radius R, its mass remaining unchanged. Which curve in the figure best gives the gravitational acceleration ag on the surface of the star as a function of radius of star during collapse?

Although a photon has no rest mass, but it possesses the inertial mass m="hf"/c^2 where h is Planck's constant , f is frequency of light and c is speed of light . Since light is deflected by a gravitational field , so it is naturally assured that photons have same gravitational behaviour as other particles. When photon is emitted from source of star of mass M and radius R, total energy of photon will be sum of hf and gravitational potential energy. At a large distance from star, the photon is beyond the star's gravitational field , so its gravitational potential energy becomes zero but its total energy remains constant. So frequency of a photon emitted from surface of a star decreases as it moves away from star. A photon in visible region of spectrum is thus shifted towards red end, and this phenomena is known as gravitational red shift. The potential energy of photon which is at surface of star is (where , M=Mass of the star , R=Radius of the star, G=Universal gravitational constant )

Although a photon has no rest mass, but it possesses the inertial mass m="hf"/c^2 where h is Planck's constant , f is frequency of light and c is speed of light . Since light is deflected by a gravitational field , so it is naturally assured that photons have same gravitational behaviour as other particles. When photon is emitted from source of star of mass M and radius R, total energy of photon will be sum of hf and gravitational potential energy. At a large distance from star, the photon is beyond the star's gravitational field , so its gravitational potential energy becomes zero but its total energy remains constant. So frequency of a photon emitted from surface of a star decreases as it moves away from star. A photon in visible region of spectrum is thus shifted towards red end, and this phenomena is known as gravitational red shift. The potential energy of photon which is at surface of star is (where , M=Mass of the star , R=Radius of the star, G=Universal gravitational constant )

An isolated triple star systerm consists of two identical stars, each of mass m and f fixed star of mass M . They revolve around the central star in the same circular orbit to radius r . The orbiting stars are always at opposite ends of a diameter of the orbit. The time period of revolution of each star around the fixed is equal to:

An isolated triple star systerm consists of two identical stars, each of mass m and f fixed star of mass M . They revolve around the central star in the same circular orbit to radius r . The orbiting stars are always at opposite ends of a diameter of the orbit. The time period of revolution of each star around the fixed is equal to:

A double star is a system of two stars of masses m and 2m , rotating about their centre of mass only under their mutual gravitational attraction. If r is the separation between these two stars then their time period of rotation about their centre of mass will be proportional to

A double star is a system of two stars of masses m and 2m , rotating about their centre of mass only under their mutual gravitational attraction. If r is the separation between these two stars then their time period of rotation about their centre of mass will be proportional to

A double star is a system of two stars of masses m and 2m , rotating about their centre of mass only under their mutual gravitational attraction. If r is the separation between these two stars then their time period of rotation about their centre of mass will be proportional to