A convex lens of focal length 20 cm and a concave lens of focal length 10 cm are placed 10 cm apart with their principal axes coinciding. A beam of light travelling parallel to the principal axis and having a beam diameter 5.0 mm, is incident on the combination. Show that the emergent beam is parallel to the incident one. Find the beam diameter of the emergent beam.

A converging lens of focal length 10cm and a diverging lens of focal length 5cm are placed 5cm apart with their principle axes coinciding. A beam of light travelling parallel to the incident one. Find the beam diameter of the emergent beam is parallel to the incident one. Find the beam diamter of the emergent beam. Alos find out the ratio fo emergent and incident intensities.

A convex lens of focal length 10cm and concave lens of focal length 20 cm are kept 5 cm apart. The focal length of the equivalent lens is

A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are joined together. The power of the combination will be

A diverging lens of focal length 20 cm and a converging lens of focal length 30 cm are placed 15 cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image formed at infinity ?

A concave lens of focal length 12 cm and a convex lens of focal length 20 cm are kept in contact with each other . Find the focal length of the combination .

If the convex lens of focal length 10 cm and a concave lens of focal length 50 cm are kept in contact with each other. What will be the power of combination ?

A light beam, passes from medium 1 to medium 2. Show that the emerging beam is parallel to the incident beam.

A light beam passes from medium 1 to medium 2. Show that the emerging beam is parallel to the incident beam.

If the convex lens of focal length 10 cm and a concave lens of focal length 50 cm are kept in contact with each other. What will be the focal length of the combination ?