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प्रश्न
At what distance from a concave mirror of focal length 25 cm should an object be placed so that the size of image is equal to the size of the object.
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उत्तर
If an object is placed at the centre of curvature of a concave mirror, the size of the image is equal to the size of the object.
Given,
focal length = 25 cm
As, center of curvature = 2 × focal length
Therefore,
center of curvature
= 2 × 25
= 50 cm
Hence, the object should be placed at 50 cm.
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संबंधित प्रश्न
Define the following term in the context of spherical mirrors:- Principal axis
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. |
A small object is placed 150 mm away from a diverging lens of focal length 100 mm.
(i) Copy the figure below and draw rays to show how an image is formed by the lens.
Figure
(ii) Calculate the distance of the image from the lens by using the lens formula.
A student obtained a sharp image of a burning candle, placed at the farther end of a laboratory table, on a screen using a concave mirror. For getting better value of focal length of the mirror, the subject teacher suggested him for focusing a well illuminated distant object. What should the student do?
(A) He should move the mirror away from the screen.
(B) He should move the mirror slightly towards the screen.
(C) He should move the mirror as well as the screen towards the newly selected object.
(D) He should move only the screen towards the newly selected object.
Choose the correct alternative and rewrite the following:
Mirror used by a dental surgeon is ..........................
Define the following term in relation to concave mirror.
Principal axis
What is the relationship between the focal length and radius of curvature?
In the following figure shows a concave mirror with its pole (P), focus (F) and centre of curvature (C). Draw a ray diagram to show the formation of the image of an object AB by the concave mirror.
The diagram below shows the parallel rays incident on a convex mirror. C is the centre of the curvature of the mirror. By drawing the paths of the reflected rays, label the focus F and hence find the focal length of the mirror.
