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A Converging Mirror Forms a Real Image of Height 4 Cm of an Object of Height 1 Cm Placed 20 Cm Away from the Mirror: (I) Calculate the Image Distance. (Ii) What is the Focal Length of the Mirror? - Science

A converging mirror forms a real image of height 4 cm of an object of height 1 cm placed 20 cm away from the mirror:

(i) Calculate the image distance.
(ii) What is the focal length of the mirror?

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Solution

A concave mirror is a converging mirror.

Distance of the object from the mirror 'u' = -20 cm
Height of the object 'ho' = 1 cm
Height of the image 'hi' = -4 cm
We have to find the distance of the image 'v' and focal length of the mirror 'f'.
Using the magnification formula, we get  
`m=h_i/h_o=-v/u` 
`-4/1=-v/-20` 
`v=20xx-4/1=-80` cm 

Thus, the distance of the image 'v' is 80 cm.

Now, using the mirror formula, we get 

`1/f=1/v+1/u` 

`1/f=1/-80+1/-20=-1/80-4/80=-5/80`  

`1/f=-1/16` 

f=-16 cm 

Thus, the focal length of the concave mirror is 16 cm.

  Is there an error in this question or solution?
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APPEARS IN

Lakhmir Singh Class 10 Physics (Science)
Chapter 4 Reflection of Light
Q 16 | Page 198
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