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प्रश्न
A converging lens has focal length of 12 cm. Calculate at what distance the object should be placed from the lens so that it forms an image at 48 cm on the other side of the lens.
उत्तर
Given,
Image distance: v = +48 cm (It is on the other side of the lens)
Focal length: f = +12 cm (It is a converging lens or convex lens)
Object distance: u =? (To be calculated)
Now, putting these values in the lens formula:-
`1/f=1/v-1/u`
`rArr1/12=1/48-1/u`
`rArr1/u=1/48-1/12`
`rArr1/u=(1-4)/48`
`rArr1/u=(-1)/16`
`rArru=-16" cm"`
Therefore, the object should be placed at a distance of 16 cm from the convex lens. The minus sign with the object distance shows that the object is on its left side.
संबंधित प्रश्न
At what distance from a concave lens of focal length 20 cm, should a 6 cm tall object be placed so that it forms an image at 15 cm from the lens ? Also determine the size of the image formed.
A student has obtained an image of a distant object on a screen to determine the focal length F1 of the given lens. His teacher, after checking the image, gave him another lens of focal length F2 and asked him to focus the same object on the same screen. The student found that to obtain a sharp image, he has to move the lens away from the screen. From this finding, we may conclude that both the lenses given to the student were :
(A) Concave and F1 < F2
(B) Convex and F1 < F2
(C) Convex and F1 > F2
(D) Concave and F1 > F2
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(b) is less than one
(c) is more than one
(d) can be more less than one depending on the position of object
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What do you understand by the term magnification?
In a reading glass what is the position of the object with respect to the convex lens used?
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