Question

an object 2cm is size infront of a concave mirror of focal length 15 cm and forms an image of an object Kept at a distance of 10cm from it Find the position nature and size of the image formed it​

Answer 1

Given :

• focal length of a concave mirror = 15 cm

• Distance of object from pole of mirror = 10 cm

• Height of object = 2 cm

To find :

• position, nature and size of the image formed

Formula used :

• 1/v + 1/u = 1/f

• m = -v/u = hi /ho

where :-

• u = distance of object from mirror
• v = distance of image from mirror
• f = focal length
• m = magnification
• hi = height of image
• ho = height of object

Solution :

First we will find position of image :-

⟹ 1/v + 1/u = 1/f

Now put :-

• u = -10
• f = -15

⟹ 1/v - 1/10 = -1/15

⟹ 1/v = 1/10 -1/15

LCM of 10 and 15 = 30

⟹ 1/v = (3-2)/30

⟹ 1/v = 1 / 30

v = 30 cm

magnification = -v/u = hi /ho

⟹ -( -30/15) = hi /2

⟹ 30/15 = hi /2

⟹ 2 = hi /2

⟹ 2 × 2 = hi

⟹ 4 = hi

Answer :

• Image is formed at a distance of 30 cm from the pole of mirror and opposite side of object.

• Image is erect , virtual and enlarged.

• Height of image is = 4 cm