The image formed by a convex spherical mirror is always:

Two lenses of power $+3.5 D$ and $-2.5 D$ are placed in contact. Find the power and focal length of the lens combination.

The image of an object formed by a plane mirror is due to which optical phenomenon?

The figure below shows a lens treated as a combination of two prisms and a glass block. $(i)$ Name the lens formed by the combination. $(ii)$ Is the lens converging or diverging? $(iii)$ Draw the refraction of two incident rays to illustrate the property of the lens mentioned by you in part $(ii).$

The formation of an image by a lens is due to which optical phenomenon?

Where should an object be placed in front of a concave mirror to obtain its image at the same position?