When an object is placed before a lens , the lens forms a virtual image for all positions of the object. Is the lens convex or concave ?

What is objective and eye-piece lens ?

A convex mirror and convex lens of radius of curvature 20 cm are placed on same axis with 30 cm separation. A point-like object is placed at 20 cm from convex lens and its image by this combination is obtained at object. What will be focal length of convex lens ?

Shown an object and its image formed by a thin lens. Then the nature and focal length of lens is

An object and a screen are fixed at a distance d apart. When a lens of focal length f is moved between the object and the screen, sharp images of the object are formed on the screen for two positions of the lens. The magnifications produced at these two positions are M_(1) "and" M_(2) -

In figure , L is half part of an equiconvex glass lens (mu=1.5) whose surfaces have radius of curvature R =40cm and its right surface is silvered . Normal to its principal axis a plane mirror M is placed on right of the lens . Distance between lens L and mirror M is b. A small object O is placed on left of the lens such that there is no parallax between final images formed by the lens and mirror. If transverse length of final image formed by lens is twice that of image formed by the mirror , calculate distance'a' in cm between lens and object.

The redius of curvature of the convex face of a plano-convex lens is 12cm and its refractive index is 1.5. a. Find the focal length of this lens. The plane surface of the lens is now silvered. b. At what distance form the lans will parallel rays incident on the convex face converge? c. Sketch the ray diagram to locate the image, when a point object is places on the axis 20cm from the lens. d. Calculate the image distance when the object is placed as in (c).

A point object is placed on the axis in front of a convex lens of focal length 30 cm. The distance of the object from the lens is 45 cm. If the lens is moved away from object by 1 mm and also the object is moved apart from the line joining the object and optical centre by 1 mm the displacement of the image has magnitude-

A lens placed between a candle and a fixed screen forms a real triply magnified image of the candle on the screen. When the lens is moved away form the candle by 0.8m without changing the position of the candle, a real image one-third the size of the candle is formed on the screen. Determine the focal length of the lens.

An unsymmetrical double convex thin lens forms the image of a point object on its axis will the position of the image change if the lens is reversed ?

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