Question

an object placed at distance of 4 centimetres in front of a convex mirror whose focal length is 5 centimetres.where is image formed​

Answer 1

Answer:

object Distance (u) = 4 cm (negative)

focal length of the lens (f) = 5 cm

we know, convex mirror always forms the virtual, upright and diminished. Also, object distance in the convex mirror os always negative where as image distance and focal length are positive.

Now, Applying the mirror's formula,

1/f = 1/v + 1/u

1/5 = 1/v +1

1/5 = (4-v) /4v

4v = 5(4-v)

4v = 20-5v

9v = 20

v = 20/9 = 2.222

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Answer 2

Answer

• Image Distance = 2.2 cm

Explanation

Given

• Object Distance = -4 cm
• Mirror = Convex Mirror
• Focal Length = 5 cm

To Find

• Image Distance = ?

Solution

So here we shall use the mirror formula which is,

1/f = 1/v + 1/u

• F = Focal Length = 5 cm
• Object Distance = u = -4 cm
• Image Distance = v = ?

Substituting the values,

»» 1/f = 1/v + 1/u

»» 1/5 = 1/v + 1/(-4)

»» 1/5 - 1/(-4) = 1/v

»» 1/5 + 1/4 = 1/v

[LCM of 5 & 4 is 20]

»» 4/20 + 5/20 = 1/v

»» {4+5}/20 = 1/v

»» 9/20 = 1/v

»» 20/9 = v

»» Image Distance = 2.2 cm