Question

a thin wire of length 10 cm is placed on the principal axis ofconcave mirror of focal length 15 cm. Centre of wire i sat 30 cm from the mirror. The length of image of wire is

Answer 1

Answer:

First value of u us is 25cm

than second value is 35 cm

Put Mirror formula

u = -25

f = -15

1/v + 1/u = 1/f

. Then

again

u = -35

f = -15

1/v + 1/u = 1/f

Subtract both value of V =

Length of image find

Thank you for

Answer 2

Given : A thin wire of length 10cm is placed on the principal axis of concave mirror of focal length 15cm. centre of wire sat 30 cm from the mirror.

To find : The length of image of wire.

solution : distance of the centre of wire from the mirror = 30cm

so, distance of the nearest point of wire, u₁ = 25cm

and distance of the farthest point of wire, u₂ = 35cm.

case 1 : u₁ = -25 cm , f = -15cm

using formula, 1/v + 1/u = 1/f

⇒1/v₁ + 1/-25 = 1/-15

⇒1/v₁ = 1/-15 + 1/25 = (-25 + 15)/15 × 25

⇒v₁ = -37.5 cm

case 2 : u₂ = -35 cm , f = -15cm

using formula, 1/v + 1/u = 1/f

⇒1/v₂ + 1/-35 = 1/-15

⇒1/v₂ = -1/15 + 1/35 = (-35 + 15)/15 × 35

⇒v₂ = -26.25 cm

so, the length of the image of wire, ∆v = |v₁ - v₂|

= |-37.5 + 26.25|

= 11.25 cm

Therefore the length of the image of wire is 11.25 cm .