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Science · 2023 · 4 marks
CBSE 2023 · Region 6 · Set 1 · Q39
A student took three concave mirrors of different focal lengths and performed the experiment to see the image formation by placing an object at…
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 distances with these mirrors as shown in the following table.
Now answer the following questions :
| Case No. | Object-distance | Focal length |
| I | $\displaystyle 45$ cm | $\displaystyle 20$ cm |
| II | $\displaystyle 30$ cm | $\displaystyle 15$ cm |
| III | $\displaystyle 20$ cm | $\displaystyle 30$ cm |
(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. Give 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.
Marking-scheme solution
(a) Real, inverted, diminished
(b) Case II
Because focal length of mirror is $\displaystyle 15$ cm, object distance is 30cm which means the object is placed at C.
(c) Dentists use concave mirrors
Because concave mirror forms erect and enlarged image when object is very close to the mirror.
(c) Case III
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.