An optical device is constructed by fixing three identical convex lenses of focal lengths 10 cm each inside a hollow tube at equal spacing of 30 cm each. One end of the device is placed 10 cm away from a point source. How much does the image shift when the device is moved away from the source by another 10 cm ?

A cylindrical tube has a length of 60 cm. Three identical convex lenses, each of focal length f = 10 cm are fixed inside the tube, one at each of the ends and one at the centre. One end of the tube is placed 10 cm away from a point source. The device casts an image of the object. How much does the image shift when the tube is moved away from the source by 10 cm.

A convex lens of foal length 30 cm and a concave lens of focal length 60 cm are placed in contact.If the object is placed 40 cm away from the combination ,, find the position of the image.

A convex lens of focal length 30 cm and a concave lens of focal length 60 cm are placed in combination. If an object is placed 40 cm away from the combination, find the position of the image.

An object is placed 20 cm from a convex lens of focal length 10 cm. The image must be-

The flat face of a plano-convex lens of focal length 10 cm is silvered. A point source placed 30 cm in front of the curved surface will produce a

The flat face of a plano-convex lens of focal length 10 cm is silvered. A point source placed 30 cm in front of the curved surface will produce a