Where should a pin be placed before a convex lens so that the image formed formed is at infinity ?

A point object is placed at a diatance of 25 cm from a convex lens of focal length 20 cm. If a glass slab of thickness t and refractive index 1.5 is inserted between the lens and the object, the image is formed at infinity. The thickness t is

An air bubble inside water. The refractive index of water is 4/3 . At what distance from the air bubble should a point object be placed so as to form a real image at the same distance from the bubble:-

Where should a person stand straight from the pole of a convex mirror of focal length 2.0 m. on its axis so that the image formed become half of his original height?

An object 25 cm high is placed in front of a convex lens of focal length 30 cm . If the height of image formed is 50 cm , find the distance between the object and the image (real and virtual)?

A convex lens of focal length 12.5 cm is used as a simple microscope. When the image is formed at infinite, Magnification is ....... (Near point for the normal vision is 25 cm).

The adjacent figure shows a thin plano-convex lens of refractive index mu_1 and a thin plano-concave lens of refractive index mu_2 , both having same radius of curvature R of their curved surfaces. The thin lens of refractive index mu_3 has radius of curvature R of both its surfaces. This lens is so placed in between the plano-convex and plano-concave lenses that the plane surfaces are parallel to each other. The focal length of the combination is

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image

Assertion:Image formed by concave lens is not always virtual. Reason:Image formed by a lens is real if the image is formed in the direction of ray of light with respect to the lens.