Define power of a lens. What is its unit?

The power of a lens is a measure of the degree of convergence or divergence of light rays falling on it. The power of a lens is defined as the reciprocal of its focal length in metres. If P denotes the power of a lens and f denotes the focal length of the lens, the power is formulated as; P = 1 f ( in metres ) The SI unit of power of lens is dioptre ( D ).

E M B I B E

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 16

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10th CBSE

IMPORTANT

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The focal length of a convex lens is $f$ . If an object is placed in front of the lens is gradually brought closer to the focus from a distance greater than $2 f$ , how will the size of the image change?

Important Questions on Light - Reflection and Refraction

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10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 17

Draw ray diagrams to describe the nature, position and relative size of the image formed by a concave lens for the object when the object is placed at infinity.

EASY

10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 17

Draw ray diagrams to describe the nature, position and relative size of the image formed by a concave lens for the object when the object is placed between infinity and optical centre of the lens.

MEDIUM

10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 18

The image of an object formed by a concave lens appears closer and smaller than the object. Explain with the help of a diagram.

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10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 19

Describe how a pen would look if you saw it through (a) convex lens, (b) a concave lens; the pen is kept close to the lenses. State the nature of image in each case.

MEDIUM

10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 20

Distinguish between convex and concave lenses.

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10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 21

Draw a ray diagram to illustrate the use of a convex lens as a magnifying glass. Why do we usually prefer a convex lens of short focal length than the one with long focal length?

MEDIUM

10th CBSE

IMPORTANT

Eduwiser's CBSE PHYSICS FOR CLASS X>Chapter 4 - Light - Reflection and Refraction>EXERCISE>Q 22

An object is placed at a distance of