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# a 10 cm long stick is kept in front of a concave mirror having focal length of 10 cm in such a way that the end of the stick closest to the pole is at a distance of 20 cm. what will be the length of the image?

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## A 10 cm long stick is kept in front of a concave mirror having focal length of 10 cm in such a way

A 10 cm long stick is kept in front of a concave mirror having focal length of 10 cm in such a way ... of 20 cm. What will be the length of the image?

## A 10 cm long stick is kept in front of a concave mirror having focal length of 10 cm in such a way

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## A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole is at a distance of 20 cm . What will be the length of the image?

Click here👆to get an answer to your question ✍️ A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole is at a distance of 20 cm . What will be the length of the image?

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A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole is at a distance of 20 cm. What will be the length of the image?

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Updated on : 2022-09-05

Consider stick AB is placed infront of a concave mirror as shown in the figure

Solution Verified by Toppr For end  A,

Object distance, u=−30 cm

focal length, f=−10 cm

Let the image A ′

of the end of the stick at point A has formed at a distance v

a ′ ​ from the mirror.

Using mirror formula,

⇒ f 1 ​ = v 1 ​ + u 1 ​ ⇒ v a ′ ​ 1 ​ = −10 1 ​ − −30 1 ​ =− 30 2 ​ v a ′ ​ =−15 cm

Object distance, u=−20 cm

focal length, f=−10 cm

Let the image B ′

of the end of the stick at point B has formed at a distance v

b ′ ​ from the mirror.

Using mirror formula,

f 1 ​ = v 1 ​ + u 1 ​ ⇒ v b ′ ​ 1 ​ = −10 1 ​ − −20 1 ​ =− 20 1 ​ ⇒v b ′ ​ =−20cm

Therefore, the length of the image  =v

a ′ ​ −v b ′ ​ =20−15=5 cm

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## Solve the following example. A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole

Solve the following example. A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole

Solve the following example.

A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole is at a distance of 20 cm. What will be the length of the image?

### SOLUTION

For end A,

u = -30 cm f = -10 cm

Let the image of the end of stick at point A is formed at a distance v from the the mirror. Therefore, using mirror formula, we have

1f=1v+1u ⇒ 1v=1-10-1-30=-230 ⇒ v = -15 cm

For end B,

u = -20 cm f = -10 cm

Let the image of the end of stick at point B is formed at a distance v' from the the mirror. Therefore, using mirror formula, we have

1f=1v′+1u ⇒ 1v′=1-10-1-20=-120 ⇒ cm v′=-20cm

Therefore, the length of the image  = v' - v = 20 - 15 = 5 cm

Concept: Spherical Mirrors

Is there an error in this question or solution?

Chapter 11: Reflection of Light - Exercise [Page 127]

Q 5.3 Q 5.2 Q 6

### APPEARS IN

Balbharati Science and Technology 9th Standard Maharashtra State Board

Chapter 11 Reflection of Light

Exercise | Q 5.3 | Page 127