Question

if the object distance is 10 and image distance is 20 then find focus​

Answer 1

$\huge {\underline{\pink{ Given:-}}}$

• Object distance ,u = -10 cm

• Imgae distance ,v = 20cm

$\huge {\underline{\green{To Find:-}}}$

• Focal length ,f

$\huge {\underline{\blue{Solution:-}}}$

We have to calculate the Focal length . Using Mirror Formula

• 1/v + 1/u = 1/f

Substitute the value we get

➨ 1/20 + 1/(-10) = 1/f

➨ 1/f = 1/20 + 1/(-10)

➨ 1/f = 1/20 - 1/10

➨ 1/f = 1-2/20

➨ 1/f = -1/20

➨ f = -20/1

➨ f = -20 cm

Therefore, the focal length is 20 cm .

Answer 2

Answer:

Given: f=15

u=−10

From mirror formula,

u

1

+

v

1

=

f

1

−10

1

+

v

1

=

15

1

v=6 cm

Image is formed 6 cm to the right of the mirror. Image formed is virtual and erect.