Question

Solution

Correct option is

45 cm are virtual images of object PQ due to reflections in A andB respectively. Since the image of object PQ due ot reflection from plane mirror A is as far behind the mirror as the object is in front of it, the image distance for the convex mirror B is Object distance  Which gives          f = 22.5 cm

Hence                   R = 2f = 45 cm

SIMILAR QUESTIONS

Q1

The radius of curvature of the convex face of a plano-convex lens is 12 cm and its refractive index is 1.5. What is the focal length of the lens?

Q2

A point object is placed at a distance of 12 cm on the axis of a convex lens of focal length 10 cm. On the other side of the lens, a convex mirror is placed at a distance of 10 cm from the lens such that the image formed by the combination coincides with the object itself. What is the focal length of the convex mirror?

Q3

Two glasses have dispersive powers in the ratio of 2 : 3. These glasses are used in the manufacture of an achromatic objective of focal length 20 cm. What are the focal lengths of the two lenses of the objective?

Q4

An object 5 cm tall is placed 10 cm from a convex mirror. What is the nature and the size of the image?

Q5

A convex mirror of radius of curvature 20 cm forms an image which is half the size of the object. How far is the object from the mirror?

Q6

How far should an object be held from a concave mirror of focal length 40 cm so as to obtain an image twice the size of the object?

Q7

A concave mirror produces a real image twice the size of the object when place at a distance of 22.5 cm from it. At what distance from the mirror should the object be placed so that the image becomes three times the size of the object?

Q8

Two objects A and B when placed in turn in front of a concave mirror of focal length 7.5 cm, give images of equal size. If A is three times the size ofB and is placed 30 cm from the mirror, what is the distance of B from the mirror?

Q9

The sun’s disc subtends an angle of 10–2 rad at the earth. What must be radius of curvature of the mirror which will produce on a screen an image of the sun 2 cm in diameter?

Q10

A concave mirror (focal length 15 cm) and a convex mirror (focal length 10 cm) are placed co-axially 70 cm apart facing each other. A 2 cm tall object is placed perpendicular to the common axis 20 cm from the concave mirror. How far from the convex mirror is the final image formed by two reflections, first at concave mirror and then at convex mirror?