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प्रश्न
An object of length 4 cm is placed in front of a concave mirror at distance 30 cm. The focal length of mirror is 15 cm.
- Where will the image form?
- What will be the length of image?
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उत्तर
O = 4 cm
u = -30 cm
f = -15 cm
From mirror formula ,
`1/"f" = 1/"v" + 1/"u"`
∴ `1/"v" = 1/"f" - 1/"u"`
∴ `1/"v" = 1/(-15) - 1/(-30) = 1/30 - 1/15`
∴ `1/"v" = (-1)/30`
∴ v = -30 cm
Hence , the image is formed at a distance of 30 cm in front of the mirror .
m = `-"v"/"u" = "I"/"O"`
∴ I = `"-OV"/"u" = (-4 xx -30)/(-30) = -4`cm
Negative sign indicates inverted image.
So, I = 4 cm
Hence , the length of the image is 4 cm.
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संबंधित प्रश्न
Explain the following term related to spherical lenses:- optical centre
Image formed by a convex ______ is always virtual and smaller in size.
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. |
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An optical device has been given to a student and he determines its focal length by focusing the image of the sun on a screen placed 24 cm from the device on the same side as the sun. Select the correct statement about the device.
(A) Convex mirror of focal length 12 cm
(B) Convex lens of focal length 24 cm
(C) Concave mirror of focal length 24 cm
(D) Convex lens of focal length 12 cm
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Define the radius of curvature.
