A convex lens has focal length of 20 cm. At what distance should be an object placed from the lens so that it forms a real image at 20 cm from the lens?

A concave lens has focal length of 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also find the magnification produced by the lens.

At what distance should be placed from a convex lens of focal length 15 cm to obtain an image three times the size of the object?

A double convex lens has 10 cm and 15 cm as its two radii of curvature.The image of an object,placed 30 cm from the lens,is formed at 20 cm from the lens on the other side.Find the refractive index of the material of the lens.Whgat will be the focal length ?What will be the focal length of the lens,if it is immersed in water of refractive index 1.33?

Where should an object be placed in front of a convex lens to get a real image of the size of the object?

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

A convex lens of focal length 20 cm is placed at a distance of 24 cm from the screen how far from the lens should an object be placed so as to from a real image on the screen. Also find the nature and magnification of the image produced.