what happens when parallel beam of light fall on concave mirror at some angle?

Answer 1

General answer:
When a parallel beam of light falls on a concave mirror, it will converge to a point on the focal plane, which is a plane perpendicular to the principal axis containing the principal focus.
Advanced answer:
Situation 1. If the parallel beam is quite narrow, then it will almost converge to a specific point on the focal plane as mentioned above.
Situation 2. If the beam is a wide beam, then due to spherical aberration (which is a defect of spherical mirrors, where wide parallel rays converge to a smaller focal distance and narrow parallel rays converge to a larger focal distance) you will find a stretch of foci forming a caustic curve. At different angles the caustic curve just moves around. You can notice the caustic curve formation at the bottom of a wet cup if you hold it such that a single light source hits the inner edges.
To reduce this spherical aberration the concave mirror can be made more parabolic.

Hope my answer helps.....

Answer 2

Parallel beam of light after reflection on a concave mirror will appear to diverge from a point ( not the focus, but )on focal plane of the mirror.

Focal plane is the plane perpendicular to the principal axis, at the focus of the mirror.

The angle of divergence will be twice the angle of incidence on the mirror.

Answer 3

That depends on the shape of the mirror. If the beams are parallel to the axis of the mirror, they converge at the focus. Otherwise, if they converge at all, it is on or near the focal plane. There's not a simple general case.

Answer 4

if you mean beams - then the departing beams will cross each other on the other side from the incoming.

Answer 5

they converge in one point i.e. focus of the mirror......