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Standard VIII

Physics

Refraction

The illuminan...

Question

The illuminance of a surface distance $10$ m from a light source is $10$ lux. The luminous intensity of the source for normal incidence will be

10^{1} C d

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10^{2} C d

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10^{3} C d

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none of these

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Solution

The correct option is C $10^{3} C d$
We have illuminance
$I = \frac{ϕ}{R^{2}}$
$⟹ ϕ = I R^{2} = 10 \times 10^{2} = 10^{3} C d$

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The illuminance of a surface distance 10 m from a light source is 10 lux. The luminous intensity of the source for normal incidence will be

The correct option is C 103CdWe have illuminanceI=ϕR2⟹ϕ=IR2=10×102=103Cd

The illuminance of a surface distance $10$ m from a light source is $10$ lux. The luminous intensity of the source for normal incidence will be

The correct option is C $10^{3} C d$
We have illuminance
$I = \frac{ϕ}{R^{2}}$
$⟹ ϕ = I R^{2} = 10 \times 10^{2} = 10^{3} C d$