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प्रश्न
A concave mirror forms a real image of an object placed in front of it at a distance 30 cm, of size three times the size of object. Find
- the focal length of mirror
- position of image.
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उत्तर
u = −30 cm
m = `I/O = 30/O = 3`
But, for real object m is negative
∴ m = −3
∵ m = `-v/u`
∴ `-v/u = -3`
∴ v = 3u
∴ v = 3 × −30
∴ v = −90 cm
Hence, the position of the image is 90 cm in front of the mirror.
From mirror formula,
`1/f = 1/v + 1/u`
∴ `1/f = 1/(-90) + 1/(-30)`
= `-1/90 - 1/30`
= `(-1 - 3)/90`
= `(-4)/90`
∴ f = −22.5 cm
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संबंधित प्रश्न
One half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer. A 4 cm tall object is placed perpendicular to its principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 15 cm. Find the nature, position and the size of the image.
What type of image is formed:
in a plane mirror?
Write the formula for a lens connecting image distance (v), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?
Draw separate diagram for the formation of virtual image of an object by a concave mirror.
For what position of object, the image formed by a concave mirror is magnified and erect?
State the kind of mirror used
(a) By a dentist,
(b) As a search-light reflector.
Find the height of the image of a body of height 1.5m in a mirror with a magnification of 1.5.
Define the term Focus of a concave mirror.
Define the term Normal.
