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The camera lens has an aperture of f and...

The camera lens has an aperture of f and the exposure time is (1/60)s. What will be the new exposure time if the aperture become 1.4f ?

A

`(1)/(42)`

B

`(1)/(56)`

C

`(1)/(72)`

D

`(1)/(31)`

Text Solution

Verified by Experts

The correct Answer is:
D
Time of exposure `prop f^(2)`
`(1)/(60)xx(1)/(1)=(t)/(1.4^(2))rArr t=0.3266 s`
`t=(1)/(31)s`.
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Knowledge Check

  • If the focal length of a lens of a camera is 5f and that of another is 2.5 f what is the time of exposure for the second if for the first one is 1/200s (where f is focal length /unit aperture)

    A
    1/200
    B
    1/800
    C
    (1/6400)
    D
    (1/3200)

  • If the focal length of a lens of a camera is 5f and that of another is 2.5 f what is the time of exposure for the second if for the first one is 1/200s (where f is focal length /unit aperture)

    A
    1/200
    B
    1/800
    C
    (1/6400)
    D
    (1/3200)

  • A thin convex lens of focal length f, has its aperture of diameter d. It forms a real iomage of intensity I. The central part of the aperture is blocked by an opaque paper of diameter (d)/(2) . What is the focal length of the lens and the intensity of image formed by the lens ?

    A
    `(f)/(2), (I)/(2)`
    B
    `f, (3I)/(4)`
    C
    `(3f)/(4), (1)/(2)`
    D
    `f, (I)/(4)`

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