Question

An object is kept on the principal axis of a concave mirror of focal length 12 cm. If the object is at a distance of 18 cm from the mirror, calculate then image distance. Determine the nature of the image formed by calculating
the magnification produced by the mirror,​

Answer 1

Given :-

• Focal length = - 12cm
• Object distance = - 18cm

To Find :-

• Image distance
• Nature of image
• Magnification

Solution :-

Apply mirror formula

→ 1/v + 1/u = 1/f

→ 1/v + (-1)/18 = -1/12

→ 1/v = 1/18 - 1/12

→ 1/v = 2 - 3/36

→ 1/v = -1/36

→ v = - 36cm

Hence,

• Image Distance is -36cm
• Nature of image = Real and inverted

★ Magnification of mirror ★

→ m = -v/u = hi/ho

→ m = -v/u

→ m = -(-36)/-18

→ m = -36/18

→ m = - 2

Hence,

• Magnification of mirror is - 2

Answer 2

Given :-

• Focal length = - 12cm
• Object distance = - 18cm

To find :-

• image distance
• Nature of image
• Magnification

Solution :-

Apply mirror formula

→ 1/v + 1/u = 1/f

→ 1/v + (-1)/18 = -1/12

→ 1/v + 1/18 -1/12

→ 1/v = 2 - 3/36

→ 1/v = -1/36

→ v = - 36cm

Hence,

• Image Distance is -36cm
• Nature of Image = Real and inverted

★ Magnification of mirror ★

→ m = -v/u = hi/ho

→ m = -v/u

→ m = -(-36)/-18

→ m = -36/18

→ m = - 2

Hence,

• Magnification of mirror is - 2