Two convex lenses 10D and 20D are combined together to form a new lens.Then what is the resultant focal length of lens

Two lenses of power 6 D and – 2 D are combined to form a single lens. The focal length of this lens will be

Two plano-convex lenses of focal lengths 20cm and 30cm are placed together to form a double convex lens. The final focal length will be

The distance between a convex lens and a plane mirror is 10 cm. The parallel rays incident on the convex lens after reflection from the mirror form image at the optical centre of the lens. Focal length of lens will be

The distance between a convex lens and a plane mirror is 10 cm. The parallel rays incident on the convex lens after reflection from the mirror forms image at the optical centre of the lens. Focal length of lens will be

A convex lens of focal length 10cm is placed 30 cm in front of a second convex lens also of th esame focal length. A plane mirror is placed after the two lenses. Where should a point object be placed in front of the first lens so that it imagees on to itself?

A convex lens, made of glass, is immersed in water. As a result, its focal length will:

Find the distance of an object from a convex lens if image is two times magnified. Focal length of the lens is 10cm

Find the distance of an object from a convex lens if image is two times magnified. Focal length of the lens is 10cm

Two plano-convex lenses of equal focal lengths are arranged as shown The ratio of the combined focal lengths is

A parallel beam of monochromatic light falls on a combination of a convex lens and a concave lens of focal lengths 15 cm and 5 cm respectively. What is the distance between the two lenses to obtain a parallel beam of light from the concave lens ?