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प्रश्न
Define the term focus of a lens.
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उत्तर
The focus of a lens (often called the principal focus) is a specific point on its principal axis where light rays parallel to the axis either converge or appear to originate from after passing through the lens.
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संबंधित प्रश्न
What is a lens?
In the diagram below, XX’ represents the principal axis, O the optical centre and F the focus of the lens. Complete the path of rays A and B as they emerge out of the lens.
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| (a) | (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 L whose foci are at F1 and F2.
- Draw two rays to locate the position of the image.
- State the position of the image with reference to the lens.
- Describe three characteristics of the image.
- Describe how the distance of the image from the lens and its size change as the object is moved towards F1.
A ray of light incident at the optical centre of lens, passes undeviated after refraction.
For an object placed at a distance 20 cm in front of a convex lens, the image is at a distance 20 cm behind the lens. The focal length of the convex lens is ______.
State the condition of the following:
A lens has both its focal lengths equal.
State the condition of the following:
A ray passes undeviated through the lens.
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.
When does a ray of light falling on a lens pass through it undeviated?
