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An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image. - CBSE Class 10 - Science

ConceptReflection of Light Image Formation by Spherical Mirrors - Concave Mirror

Question

An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.

Solution

Object distance, u= – 27 cm
Object height, h= 7 cm
Focal length, f = – 18 cm
According to the mirror formula,

1/v-1/u=1/f

1/v=1/f-1/u=-1/18+1/27=-1/54

v=-54 cm

The screen should be placed at a distance of 54 cm in front of the given mirror.

h_1/h=-v/u

The negative value of magnification indicates that the image formed is real.

h_1/7=-54/27

h1=7 x (-2)= -14 cm

The negative value of image height indicates that the image formed is inverted.

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NCERT Solution for Science Textbook for Class 10 (2019 to Current)
Chapter 10: Light – Reflection and Refraction
Q: 15 | Page no. 186

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Solution An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image. Concept: Reflection of Light - Image Formation by Spherical Mirrors - Concave Mirror.
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