A lens forms an erect image for all positions of an object in front of it. Is the lens convex or concave ?

A convex lens forms an image of an object on a screen. The height of the image is 9 cm . The lens is now displaced until an image is again obtained on the screen. Then height of this image is 4 cm . The distance between the object and the screen is 90 cm.

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 focal length of a concave mirror is 30 cm.Find the position of the object in front of the mirror,so that the image is three times the size of the objects.

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 ?

Assertion:- The image focus ( 2^(nd) focus) and the object focus ( 1^(st) focus) are on the oppostie side of the biconvex or biconcave lens. Reason:- The radii of curvature of a biconvex lens and biconcave lens are on the opposite side of the lens.

In an optics experiment, with the position of the object fixed, a student varies the position of a convex lens and for each position, the screen is adjusted to get a clear image of the object. A graph between the object distance u and the image distance v, from the lens, is plitted using the same scale for the two axes. A straight line passing through the origin and making an angle of 45^circ with x-axis meets the experimental curve at P. The coordinates of P will be.

A thin convex lens from a real Image of a certain object 'p' times it size .The size of real image become 'q' times that of object when the lens is moved nearer to the object by a distance 'a' find focal length of the lens?

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-

Is power negative or positive for concave lens ?

Graph of position of image vs position of point object from a convex lens is shown. Then, focal length of the lens is