Reflection At Spherical Surface

A concave mirror of the focal length is placed at a distance of from a convex lens of focal length ${\mathrm{}}_{}$. A beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance must be equal to:

1.

2.

3.

4.

An object is placed at a distance of from a concave mirror of a focal length of If the object is displaced through a distance of towards the mirror, the displacement of the image will be:

1.	away from the mirror.
2.	away from the mirror.
3.	towards the mirror.
4.	towards the mirror.

An object is placed on the principal axis of a concave mirror at a distance of ( is the focal length). The image will be at:

1.		2.
3.		4.