Question

For a concave mirror of focal length 'f', the minimum distance between the object and its real image is :

A plane wave is incident on a concave mirror of radius of curvature R. The reflected wave is a spherical wave of radius :

Draw a labelled ray diagram showing the formation of the image at infinity by an astronomical telescope.

A telescope consists of an objective of focal length 150 cm and an eyepiece of focal length 6·0 cm. If the final image is formed at infinity, then calculate : (I) the length of the tube in this adjustment, and (II) the magnification produced.