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Refractive Index of a Prism

A point sourc...

Question

A point source of $100$ candela is held $5$ $m$ above a sheet of blotting paper which reflects $75$ % of light incident upon it. The illuminance of blotting paper is

A

4

phot

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B

4

lux

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C

3

phot

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D

3

lux

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Solution

The correct option is B $4$ lux
Illuminance = $\frac{L}{d^{2}}$
$\frac{100}{5^{2}}$ = 4 lux

Answer. B) 4 lux

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