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प्रश्न
उत्तर
Focal length is the distance measured from the optical centre to the focus. The symbol for it is f.
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संबंधित प्रश्न
The diagram below shows a lens as a combination of a glass slab and two prisms.
- Name the lens formed by the combination.
- What is the line XX’ called?
- Complete the path of the incident ray AB after passing through the lens.
- The final emergent ray either meets XX’ at a point or appears to come from a point on XX’. Label it as F. What is this point called?
In the following figure (a) and (b), F1 and F2 are positions of the two foci of thin lenses. Draw the path taken by the light ray AB after it emerges from each lens.
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| (a) |
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| (b) |
Distinguish between a real and a virtual image.
The diagram given below shows the position of an object OA in relation to a converging lens whose foci are at F1 and F2.
Describe three characteristic of the image.
A ray of light incident at the optical centre of lens, passes undeviated after refraction.
In the following diagram ., the object and the image formed by the respective lenses are shown. Complete the ray diagram, and locate the focus. Find the focal length of the lens.
Make the rrect choices in the following items :
An object is placed 50 cm from a connverging lens of focal length 30 cm. The image produced would be
Define the term 'focus' of a lens.
Fig. shows two rays of light Op and OQ coming from an object at the bottom of a pond, incident on the water surface.
(a) Mark on the diagram
(i) The angle of incidence of ray OP,
(ii) The angle of refraction of ray Op,
(iii) The position of image of the object as seen from above.
(iv) An approximate path of the ray OQ.
(b) Explain, why do the rays of light change directions on passing from water to air.
(c) A fish in water sees everything outside the water by rays of light entering its eye in a small cone of light. Draw a diagram and explain how does this happen.
How will you differentiate between a convex and a concave lens by looking at a printed page?
