Are photon spheres stable?

The photon sphere is said to be stable if the circular orbits are stable circular orbits and unstable if unstable circular orbits.

What is the photon sphere of a black hole?

The photon sphere is a region near a black hole where the gravity is so strong that light itself can orbit around the black hole. The orbits in that region are unstable; the photons can loop around the black hole a few times, but they will not stay forever.

What happens to a photon when it enters a black hole?

Once a particle of light (‘photon’) passes the ‘event horizon’ of a black hole, it can no longer escape, but there’s nothing to suggest that it is destroyed. Like matter, the photon is rapidly sucked towards the ‘singularity’ at the centre of the black hole, where a huge mass is packed into an infinitely small space.

Can light escape the photon sphere?

In other words, any photon that approaches from distant space will be captured if its path goes inside the photon sphere at all. However, a photon emitted on a radial trajectory from an object between the event horizon and the photon sphere can escape.

How can a photon have zero mass?

Why do photons have no mass? In short, the special theory of relativity predicts that photons do not have mass simply because they travel at the speed of light. This is also backed up by the theory of quantum electrodynamics, which predicts that photons cannot have mass as a result of U(1) -gauge symmetry.

Are black holes holes or spheres?

A black hole is a sphere in the sense that everything that goes within its Schwarzschild radius (the distance from the center of the black hole to the event horizon) cannot escape its gravity. Thus, there is a dark sphere around the infinitely dense center, or singularity, from which nothing can escape.

Can photons escape a black hole?

Black holes are regions in space-time where gravity’s pull is so powerful that not even light can escape its grasp. However, while light cannot escape a black hole, its extreme gravity warps space around it, which allows light to “echo,” bending around the back of the object.

Why is the centripetal force zero in circular motion?

Without it, the circular motion is not possible. The work done by the centripetal force is zero because the displacement of the particle (tangential) is perpendicular to the direction of the centripetal force (radial) i.e. there is no displacement in the direction of the centripetal force.

What happens to the particles at the bottom of a centrifuge?

In the centrifuge, the tube containing liquid along with the suspended particles is whirled in a horizontal circle. Dense particles are acted upon by a centrifugal force. Hence they get accumulated at the bottom, which is outside while rotating. This is because buoyant force towards the center is greater for the lighter particle.

Why is centrifugal acceleration constant at the center of the Earth?

Because the centrifugal acceleration is nearly constant in time and points outward, away from Earth’s axis of rotation, we usually combine it formally with the gravitational force, which points toward Earth’s center. We replace g in Eq. (7.6) with an effective gravity g, which has a weak dependence on latitude.

What is the application of centrifugal force in physics?

The concept of centrifugal force can be applied in rotating devices, such as centrifuges, centrifugal pumps, centrifugal governors, and centrifugal clutches, and in centrifugal railways, planetary orbits and banked curves, when they are analyzed in a rotating coordinate system.