Chapter 10: Reflection and Refraction- Exercise- 4

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Chapter 10: Reflection and Refraction

Class: X

Exercises 4

 

Question 1

Define 1 diopter of power of a lens.

Answer 1

1 diopter of power of a lens is equal to the reciprocal of the focal length measured in metres that is whose focal length is 1 meter.

Question 2

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it.

Where is the needle placed in front of the convex lens if the image is equal to the size of

the object? Also, find the power of the lens.

 

Answer 2

When an object is placed at the centre of curvature of a convex lens, its image is formed at the centre of curvature on the other side of the lens. An inverted image of the same size is formed, as shown in the given figure

 

Question 3

Find the power of a concave lens of focal length 2 m.

 

Answer 3