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When we do calculation for image locatio...

When we do calculation for image location from spherical mirrors then normally we consider paraxial rays only, because paraxial rays

A

make calculations easier

B

are easier for geometrical analysis

C

contain most of the light intensity that is incident on mirror

D

can form point image for a point source

Text Solution

Verified by Experts

The correct Answer is:
D
Defects like spherical aberrations are minimum for paraxial rays and thus these rays which are very close to principal axis are able to form sharp point images for point sources.
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Rays parallel to principal axis, incident on the spherical mirror at different heights from principal axis are focused at different points. And due to this reason we cannot define unique focus. This is known as spherical aberration. Angle of incidence theta shown in figure depends on the height of ray above principal axis. Focal length of spherical mirror can be easily written in terms of angle theta shown in figure as follows : f = R- (R)/(2)sec theta Here R is radius of curvature of mirror. The light rays which are very close to principal axis are known as paraxial rays and rays far away from principal axis are called marginal rays. For paraxial rays focal length is approximately

MODERN PUBLICATION-RAY OPTICS AND OPTICAL INSTRUMENTS-OBJECTIVE TYPE QUESTIONS (A. MULTIPLE CHOICE QUESTIONS)
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  2. When light rays are incident on a thick transparent slab then these ra...

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  3. When we do calculation for image location from spherical mirrors then ...

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  4. Consider a situation when light ray is travelling from optically dense...

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  5. Image formed by a convex mirror is

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  6. The image formed by a convex lens

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  7. A medium of refractive index mu is separated from air using a plane su...

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  8. A converging lens forms a real image I on its optic axis. A rectangula...

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  9. Find the focal length of plano-convex lens of material having refracti...

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  10. A piece of glass is not visible in a colourless transparent liquid. It...

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  11. There is a sphere of radius R and refractive index mu. At what distanc...

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  12. Which of the following depend on whether rays are paraxial or not for ...

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  13. Screen is placed at a distance 60 cm from an object. A convex lens of ...

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  14. An air bubble inside water. The refractive index of water is 4/3 . At ...

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  15. An object is kept at a distance 20 cm from a convex mirror of focal le...

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  16. A point source of light is kept on the surface of a sphere and it is f...

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  17. Two concave lenses are kept in contact and magnitude of equivalent foc...

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  18. Focal length of a double convex lens is 20 cm in air. If this lens is ...

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  19. A thin lens is made of glass of refractive index 1.6. Both the surface...

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  20. Two thin concave lenses of focal lengths 10 cm and 30 cm and a thin co...

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