A lens forms a sharp image on a screen. On inserting a parallel sided glass slab between the lens and the screen, it is found necessary to move the screen a distance `d` away the lens in order for the image to be sharp again. If the refractive index of the material of the slab is `mu`, the thickness of the slab is

A converging beam of light forms a sharp image on a screen. A lens is placed in the path of the beam at 10 cm from the screen. It is found that the screen has to be moved 8 cm further away from the lens to obtain a sharp image. Find the focal length and nature of the lens.

A ocnverging bem of light forms of a sharp image on a screen. lens is placed in the path of the beam at 10 cm from the screen.It si found that screen has to be moved 8 cm further away from the lens to obtain a sharp image.Find the focal length and natrue of the lens.

A lens with a focal length of f=30 cm produces on a screen a sharp image of an object that is at a distance of a=40 cm from the lens. A plane parallel plate with thickness of d=9 cm is placed between the lens and the object perpendicular to the optical axis of the lens. Through what distance should the screen be shifted for the image of the object to remain distinct? The refractive index of the glass of the plate is mu=1.8.

A lens with a focal length of f=30 cm produces on a screen a sharp image of an object that is at a distance of a=40 cm from the lens. A plane parallel plate with thickness of d=9 cm is placed between the lens and the object perpendicular to the optical axis of the lens. Through what distance should the screen be shifted for the image of the object to remain distinct? The refractive index of the glass of the plate is mu=1.8.

An object 240 cm in front of a lens forms a sharp image on a screen 12 cm behind the lens. A glass slab 1 cm thick, having refractive index 1.50 is placed between the lens and the screen with its refracting faces perpendicular to the principal axis of the lens. (a) By how much distance the object must be moved so as to again cast a sharp image on the screen? (b) Another identical glass slab is interposed between the object and the lens. How much further the object shall be moved so as to form a sharp image on the screen.