Lens And Its Types
Lens And Its Types
Lens
A lens is a piece of transparent material with two refracting surfaces such that at least one is curved and refractive index of a material is different from that of the surroundings.
Convex lens: A thin spherical lens with refractive index greater than that of surrounding behaves as a convergent or convex lens i.e. converges parallel rays. Its central (i.e. paraxial) portion is thicker than marginal one.If the refractive index of of the lens is more than the refractive index of the surroundings it acts as converging lens i.e.
If then Converging Lens
But if the refractive index of of the lens is less than the refractive index of the surroundings it acts as diverging lens i.e.
If then Diverging Lens.
The various types of Convex lens are:
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1. Double Convex Lens: When both the refracting surfaces are convex surfaces.with same radius of curvature for both surfaces It is called double convex lens.
2. Bi-Convex Lens: When both the refracting surfaces are convex surfaces but the radius of curvature is different for both surfaces. It is called bi-convex lens.
3. 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.
4. 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. .If the refractive index of the material of lens is more than the refractive index of the surroundings it acts as diverging lens i.e. If But if the refractive index of of the material of lens is less than the refractive index of the surroundings it acts as converging lens i.e. If The various types of Concave lens are: 1. Double Concave Lens: When both the refracting surfaces are concave surfaces with same radius of curvature for both surfaces. It is called double concave lens.
2. Bi-Concave Lens: When both the refracting surfaces are concave surfaces but the radius of curvature is different for both surfaces. It is called bi-concave lens.
3. 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.
4. 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) A thin spherical lens which is thicker at the middle than the edges behaves as a divergent lens. (b) When one of the refracting surface of a lens is plane and the other refracting surfaces is concave surfaces. It is called plano - concave lens. | |||
| Right Option : B | |||
| View Explanation | |||
When one of the refracting surface of a lens is plane and the other refracting surfaces is concave surfaces. It is called ____________________ . | |||
| Right Option : A | |||
| View Explanation | |||
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