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प्रश्न
What are the three principal rays that are drawn to construct the ray diagram for the image formed by a lens? Draw diagrams to support your answer.
उत्तर
(i) A ray of light incident at the optical centre O of the lens passes undeviated through the lens.
Convex lens
Concave lens
(ii) A ray of light incident parallel to the principal axis of the lens, after refraction passes through the second focus F2 (in a convex lens) or appears to come from the second focus F2 (in a concave lens).
Convex lens
Concave lens
(iii) A ray of light passing through the first focus F1 (in a convex lens) or directed towards the first focus F1 (in a concave lens), emerges parallel to the principal axis after refraction.
Convex lens
Concave lens
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संबंधित प्रश्न
The distance between principal focus and optical centre of the lens is _________.
- diameter
- focal length
- principal axis
- optical centre
Define focal length of a divergent lens.
An image formed by a concave ______ cannot be obtained on a screen.
A concave lens always forms a virtual image.
A real image cannot be obtained on a screen.
State two differences between a convex and a concave lens.
Write the new Cartesian sign convention for spherical lenses.
If a spherical lens has a power of, −0.25 D, the focal length of this lens will be :
(a) −4 cm
(b) −400 mm
(c) −4 m
(d) −40 cm
A convex lens forms an image of an object equal to the size of the object. Where is the object placed in front of the lens?
Which diagram shows image formation of an object on a screen by a converging lens?
