Question

a concave mirror having radius of curvature 40cm is placed in front of and illuminated point source at a distance of 30 cm from it then the location of the images
a) 60 cm from the mirror on the opposite side of the object
b) 60 cm from the mirror on the same side of the object
c) 30 cm from the mirror on the same side of the object
​

Answer 1

Answer:

Correct option is (b)

• Image will be formed 60 cm from the mirror on the same side of the side of object.

Explanation:

Given,

• Radius of curvature of Concave mirror, R = -40 cm
• Location of object, u = -30 cm

To find,

• Location of Image, v =?

So,

Using relation

→ Radius of curvature = 2 × ( focal length )

→ R = 2 f

→ f = R / 2

→ f = -40 / 2

→ f = -20 cm

• so, focal length of concave mirror is -20 cm.

Now,

Using Mirror formula

→ 1/f = 1/v + 1/u

→ 1/(-20) = 1/v + 1/(-30)

→ 1/v = 1/(-20) + 1/(30)

→ 1/v = (-3 + 2)/60

→ 1/v = -1 / 60

→ v = -60 cm

Therefore,

• Image will be formed at 60 cm from the mirror on the same side of the side of object.

And thus,

OPTION (b) is correct.