What is focal length and power of a rectangular glass slab ?

The power of a rectangular glass slab is zero .

What is power of a parallel faced glass slab?

What is the focal length and the power of a plane mirror?

What is focal length of a lens of power 2.5 D ?

What is the power and focal length- of a parallel glass slab?

Why is there no dispersion of light refracted through a rectangular glass slab ? Give reason.

Why is there no dispersion of light refracted through a rectangular glass slab ?

A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 10 cm. What is the focal length and power of the combination ?