(a) A security mirror used in a big showroom has radius of curvature 5 m. If a customer is standing at a distance of 20, from the cash counter, find the position, nature and size of the image formed in the security mirror.

(b) Neha visited a dentist in his clinic. She observed that the dentist was holding an instrument fitted with a mirror. State the nature of this mirror and reason for its use in the instrument used by dentist.

OR

Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose.

(i) State the nature of the lens and reasons for its use.

(ii) Where should the palmist place/hold the lens so as to have a real and magnified image of an object?

(iii) If the focal length of this lens is 10 cm, the lens is held at a distance of 5 cm from the palm, use lens formula to fine the position and size of the image.

(a) The focal length of the convex mirror is 2.5 m

The customer is 20 m away from the mirror, u = -20 m (as per sign convention)

Using lens formula

Show the image will be formed at a distance of 20/9 m.; the image will be diminished, virtual and erect.

(b) Concave mirrors are used as they converge the reflecting light at the focus. Also the object kept at a distance less than the focal length of the mirror produces enlarged, erect and virtual images of the object; which enables the doctor to clearly see the image of the tooth or the part of the mouth that is being inspected.

OR

(i) Convex lens is used by the palmist to get an enlarged image of the palm revealing the details even more clearly for him when placed real close to the object.

(ii) There are two cases for which a real and magnified image of object is obtained in convex lens-

a. When the object is placed at the focus of the lens.

b. When the object is placed between F and 2F of the lens.

(iii) f= 10

u = - 5

By lens formula

v = -10 cm

The size of the image will be,

The height of the image is twice that of the object.