Question

21.
Aconcave mirror is used for image formation for different positions of an
object. What inferences can be drawn about the following when an object
is placed at a distance of 10 cm from the pole of a concave mirror of focal
length 15 cm ?
Position of the image
(b) Size of the image
Nature of the image
Draw a labelled ray diagram to justify your inferences.​

Answer 1

Answer:

Position of image is 30cm, size of image is greater by 3cm and it is virtual and erect.

Explanation:

position of object (u) = -10cm

focal length (f) = -15cm

(i) Position of Image (v) :

Using mirror formula :

   1/v + 1/u = 1/f

   1/(v) + 1/(-10) = 1/(-15)

   1/v = -1/15 + 1/10

   1/v = 5/150 = 1/30

   so, v = 30  cm

(ii) size of image :

   using magnification formula

   m = h(image)/h(object)

       = or -v/u = -30/-10 = 3cm

Since the magnification is greater than 1 so, the image formed is larger in size by 3cm

(iii)nature of image :

   Image will be virtual and erect as its position is +30 cm i.e. behind the mirror in this case.

RAY DIAGRAM IS AS FOLLOWED :