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Question
Explain the following term related to spherical lenses: focal length
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Solution
Focal Length:-
The focal length of a lens is the distance between optical centre and principal focus of the lens.
RELATED QUESTIONS
Match the items given in Column I with one or more items of Column II.
| Column I | Column II | ||
| (a) | A plane mirror | (i) | Used as a magnifying glass. |
| (b) | A convex mirror | (ii) | Can form image of objects spread over a large area. |
| (c) | A convex lens | (iii) | Used by dentists to see enlarged image of teeth. |
| (d) | A concave mirror | (iv) | The image is always inverted and magnified. |
| (e) | A concave lens | (v) | The image is erect and of the same size as the object. |
| (vi) | The image is erect and smaller in size than the object. |
Define the Focal length of a spherical mirror
Name the two kinds of spherical mirrors and distinguish between them.
What is meant by magnification? Write its expression. What is its sign for the (a) real (b) virtual, image?
The sun is seen before the sunrise and after the sunset.
An object 10 cm high is placed at a distance of 20 cm in front of a spherical mirror of focal length 25 cm. By scale drawing find the nature, position, and magnification of the image in the following case:
Concave mirror
The spherical mirror used in a beauty parlour as make-up mirror is _______.
