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Questions and Answers
What happens to the rays of light after refracting through a convex lens?
A concave lens always converges the rays of light after refraction.
False
What is the central part of a lens similar to?
A rectangular glass slab
The radius of a sphere whose surface forms a part of a lens is called the ______________________.
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Match the following terms related to lenses with their definitions:
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A concave lens is always thicker in the middle and thinner at the edge.
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What is the function of a lens in optical instruments?
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What is the name of the lens that is thick in the middle and thin at the edge?
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A lens can be assumed to be made by the combination of many ______________ in correct order.
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Match the following types of lenses with their characteristics:
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Study Notes
Lenses and Their Characteristics
- A lens is an optical device made up of a transparent medium bounded by spherical surfaces, typically made of glass or plastic.
- Lenses are of two types: convex lens and concave lens.
Convex Lens
- A convex lens is thick in the middle and thin at the edge.
- When parallel rays of light fall on a convex lens, they converge at a point after refraction.
- A convex lens is also called a converging lens.
- Examples of convex lenses include biconvex lens, planoconvex lens, and concavo-convex lens.
- The human eye contains a natural convex lens.
Concave Lens
- A concave lens is thin in the middle and thick at the edge.
- When parallel rays of light fall on a concave lens, they diverge after refraction, appearing to diverge from a point.
- A concave lens is also called a diverging lens.
- Examples of concave lenses include biconcave lens, planoconcave lens, and convexo-concave lens.
Lens as a Group of Prisms
- A lens can be assumed to be made up of a combination of many prisms in correct order.
- A convex lens consists of prisms in the upper half with their bases inward and prisms in the lower half with their bases outward.
- The parts of the lens bend the incident light, with the central part acting like a rectangular glass slab, allowing light to travel straight through.
- A concave lens can also be considered as composed of the combination of prisms, but with the bases of prisms opposite to those of a convex lens.
Terminology Related to Lenses
- Centre of curvature refers to the center of the sphere of which the lens is a part.
- Radius of curvature refers to the radius of the sphere whose surface forms a part of a lens.
- Principal axis refers to the imaginary line that joins the two centers of curvature.
- Focal length is the distance between the center of curvature and the point where parallel rays of light converge or diverge after refraction.
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Description
Learn about the importance of lenses in camera, spectacles, microscope, telescope and human eye. Discover how lenses help in clear visibility of objects and form images on the retina.
