A properly exposed photograph is taken at f/16 and 1/120s. What lens opening is required if the shutter speed is 1/60s

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A properly exposed photograph is taken at f/16 and 1/120s. What lens opening is required if the shutter speed is 1/60s

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Adela 5 months 2021-08-10T05:54:53+00:00 1 Answers 15 views 0

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    2021-08-10T05:56:30+00:00

    Answer:

    f / 8

    Explanation:

    The f-number is the ratio of the lens’s focal length to its diameter and is a measure of the intensity of the light reaching the CCD. The smaller the greater the intensity of the light

               I = D / f

               f-number = f / D

               I = 1 / f-number

    the energy deposited in the CCD is proportional to the intensity of the light and the exposure time (Δt)

              E = I Δt

              E = 1 /f-number   Δt

    in the exercise they indicate that the system is well exposed (the image is sharp and clear) for fo-number = f / 16

            Δt = exposure time = 1/120 s

            E =   \frac{1}{120} \ \ \frac{1}{fo-number}  

               

    indicate that the exposure time has been changed to Δt = 1/60 s, which should be the f₁-number

            E = \frac{1}{60} \ \ \frac{1}{f_1-number}

    the energy deposited must be the same per location we can equal the expressions

              \frac{1}{120} \ \frac{1}{f_o-number} = \frac{1}{60} \ \frac{1}{f_1-number}

             f₁-number = \frac{60}{120} \ \ \frac{1}{fo-number}

             

             f₁-number = ½  16

             f₁-number  = 8

    so the system should be set to f / 8

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