Lens And Its Types
Lens And Its Types
A lens is a piece of transparent material with two refracting surfaces such that at least one is curved and the material of lens is different from that of the surroundings.
Convex lens:
A thin spherical lens which is thicker at the middle than the edges behaves as a convergent or convex lens i.e. it converges parallel rays. Depending on the type of two surfaces they can be further classified as:
1. Double Convex Lens: When both the refracting surfaces are convex surfaces. It is called double convex lens.
2. Plano - Convex Lens: When one of the refracting surface is plane and the other refracting surfaces is convex surfaces. It is called plano - convex lens.
3. Concavo Convex Lens: When one of the refracting surface is a concave surface and the other refracting surfaces is convex surfaces. It is called concavo convex lens.
Concave lens:
If the central portion of a lens is thinner than marginal, it diverges parallel rays and behaves as a divergent or a concave lens.
1. Double Concave Lens: When both the refracting surfaces are concave surfaces. It is called double concave lens.
2. Plano - Concave Lens: When one of the refracting surface is plane and the other refracting surfaces is concave surfaces. It is called plano - concave lens.
3. Convexo Concave Lens: When one of the refracting surface is a concave surface and the other refracting surfaces is convex surfaces. It is called convexo concave lens.
Which of the following are correct ? (a) When one of the refracting surface is a concave surface and the other refracting surfaces is convex surfaces. It is called Plano convex lens . (b) If the central portion of a lens is thinner than marginal, it diverges parallel rays and behaves as a divergent or a concave lens. (c) When both the refracting surfaces are concave surfaces. It is called double concave lens. | |||
| Right Option : B | |||
| View Explanation | |||
Which of the following are correct ? (a) When both the refracting surfaces of a lens are convex surfaces. It is called double convex lens. (b) Convex lens when one of the refracting surface is plane and the other refracting surfaces is convex surfaces. It is called plano - convex lens. | |||
| Right Option : C | |||
| View Explanation | |||
When both the refracting surfaces are concave surfaces. It is called _________________ . | |||
| Right Option : C | |||
| View Explanation | |||
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