Two lenses of focal lengths 6cm and 50 cm are used in construction of a telescope. Which lens will be used as an objective and why?

Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combinations is

Two convex lenses of focal length 1.5 cm and 9 cm are arranged to form a microscope . A small object is placed 1.8 cm from the objective. If the image appears to be 37.5 cm from the eyepiece, what will be the distance between the objective and the eyepiece ?

Thin converging lenses of focal lengths 2 cm and 10 cm are used respectively as the objective and the eyepiece of a microscope. The distance between the optical centre of the lenses is 26 cm . If an object is placed at a distance of 2.25 cm from the objective , find the position and magnification of the final image.

The focal length of a lens is -50 cm. The nature and power of the lens is

In an astronomical telescope, focal length of the objective is made

An object is placed 30 cm away from a convex lens of focal length 10 cm and a sharp image is formed on a screen. Now a concave lens is placed in contact with the convex lens. The screen now has to be moved by 45 cm to get a sharp image again. The magnitude of focal length of the concare lens is (in cm)

In an astronomical telescope , focal length of the objective is made