The magnification of a real image formed by a concave mirror is always ...

For what position of the object does a concave mirror form a real and diminished image?

Where is the image formed when an object is placed anywhere in front of a concave lens?

The figure below shows an object $AB$ placed on the principal axis of a lens $L$. The two foci of the lens are $F_1$ and $F_2$. The image formed by the lens is erect,virtual and diminished. Copy the diagram and answer the following questions: $(i)$ Draw the outline of the lens $(L)$ used. $(ii)$ Draw a ray from $B$ passing through $O$. Show the ray after refraction by the lens. $(iii)$ Draw a ray of light starting from $B$,which after passing parallel to the principal axis,is incident on the lens and emerges after refraction from it. $(iv)$ Locate the final image formed.

Which of the following is a part of a spherical mirror?

What is the speed of light waves in a vacuum in units of $km/s$?