To find focal length of a Concave Mirror
 1) A thin lens and spherical mirror, each has a focal length of +25cm. Both are convex. Both are concave. The lens is convex and the mirror is concave. The lens is concave and the mirror is convex.

 2) A convex lens of focal length f, forms the image of an object equal in size of the object. The object is placed at a distance greater than 2f. less than f. equal to 2f. between f and 2f.

 3) A parallel beam of light falls on a mirror. All the rays of the beam after reflection, actually intersect at a point. The mirror is a : plane mirror. convex mirror. concave mirror. none of the above.

 4) A real image : is formed when reflected rays dont actually meet but appear to diverge from a point. cannot be obtained on a screen. can be obtained on a screen. is always erect.

 5) An object 2.0 cm in size is placed 20.0 cm in front of a concave mirror of focal length 10.0 cm. Find the distance from the mirror at which a screen should be placed in order to obtain a sharp image. What will be the size and nature of the image formed? image distance 3 cm real ,inverted same size as object. image distance 2 cm real ,inverted same size as object. image distance 4 cm imaginary ,erect, larger size than object. image distance 2 cm imaginary ,erect, larger size than object.