A candle is kept at a distance of 90 cm from a curtain. Convex objects placed between them at a focal length of 20 cm.

An object is placed at a distance of 30 cm from a convex lens of focal length 20 cm.

An object 50 cm tall is placed on the principle axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.

An object is kept at a distance 20 cm from a convex mirror of focal length 20 cm. The image will form at

What is the position of image when an object is placed is at a distance of 10 cm from a convex lens of focal length 10 cm?

A point object is placed at a distance of 20cm from a thin plano-convex lens of focal length 15cm If the plane surface is silvered.the image will form at

An object 4 cm high is placed at a distance of 10 cm from a convex lens of focal length 20 cm. Find the position, nature and size of the image.