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Question
Draw the following diagram in your answer book and show the formation of image with the help of suitable rays:
Solution
Using the following rules for image formation:
- A ray of light that is parallel to the principal axis of a concave mirror passes through its focus after reflection, and
- A ray of light passing through the focus of a concave mirror becomes parallel to the principal axis after reflection,
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RELATED QUESTIONS
Fill in the following blank with suitable word:
Parallel rays of light are reflected by a concave mirror to a point called the ..........
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between its pole and focus
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State one use of concave mirror bases on the formation of image as in case (i) above.
The focal length of a small concave mirror is 2.5 cm. In order to use this concave mirror as a dentist's mirror, the distance of tooth from the mirror should be:
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A student took three concave mirrors of different focal lengths and performed the experiment to see the image formation by placing an object at different distance with these mirrors as shown in the following table.
| Case No. | Object-distance | Focal length |
| I | 45 cm | 20 cm |
| II | 30 cm | 15 cm |
| III | 20 cm | 30 cm |
Now answer the following questions:
(a) List two properties of the image formed in Case I.
(b) In which one of the cases given in the table, the mirror will form real image of same size and why?
(c) Name the type of mirror used by dentists. Given reason why do they use such type of mirrors.
OR
(c) Look at the table and identify the situation (object distance and focal length) which resembles the situation in which concave mirrors are used as shaving mirrors? Draw a ray diagram to show the image formation in this case.
