Question

The focal length of convex mirror is 20 cm, an object is placed at the distance of 40 cm.​

Answer 1

Given

• Mirror Used = Convex
• Object Distance = -40 cm
• Focal length = 20 cm

To Find

• Image Distance

Solution

☯ Mirror Formula ; 1/f = 1/v + 1/u

• Note that fora convex mirror image distance is negative and the focal length is positive

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✭ According to the Question :

→ 1/f = 1/v + 1/u

→ 1/20 = 1/v + 1/-40

→ 1/20 = 1/v - 1/40

→ 1/20 + 1/40 = 1/v

→ 2/40 + 1/40 = 1/v

→ (2+1)/40 = 1/v

→ 3/40 = 1/v

→ v = 40/3

→ v = 13.3 cm