A lens of focal length 20cm is used to produce a ten times magnified image of a film slide on a screen. How far must the slide be placed from the lens ?

Sudha finds out that the sharp image of the window pane of her science laboratory is formed at a distance of 15cm from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens?

A 2.0cm tall object is place perpendicular to the principal axis of a concave lens of focal length 15cm. At what distance from the lens, should the object be placed so that it forms an image 10cm from the lens? Also find the nature and the size of image formed.

An object is placed at a distance of 4cm from a concave lens of focal length 12cm. Find the position and nature of the image.

A convex lens produces an inverted image magnified three times of an object placed at a distance of 15cm from it. Calculate focal length of the lens.

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

How is the refractive index of a medium related to the speed of light? Obtain an expression for refractive index of a medium with respect to another in terms of speed of light in these two media?

A concave lens of 20cm focal length forms an image 15cm from the lens. Compute the object distance.

A dentist’s mirror has a radius of curvature of 3cm. How far must it be placed from a small dental cavity to give a virtual image of the cavity that is magnified five times?

A bright object 50mm high stands on the axis of a concave mirror of focal length 100mm and at a distance of 300mm from the concave mirror. How big will the image be?