The maximum illumination on a screen at a dis | vedclass

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(A) The illumination $E$ at a distance $r$ from a point source of luminous intensity $I$ is given by $E = \frac{I}{r^2}$.Given $E = 25\, lux$ and $r =

Vedclass · Accepted Answer

$1256\, lumen$

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(A) The illumination $E$ at a distance $r$ from a point source of luminous intensity $I$ is given by $E = \frac{I}{r^2}$.Given $E = 25\, lux$ and $r = 2\, m$,we find the luminous intensity $I$:$I = E 	imes r^2 = 25 	imes (2)^2 = 25 	imes 4 = 100\, candela$.The total luminous flux $\phi$ emitted by a point source is given by $\phi = 4\pi I$.Substituting the value of $I$:$\phi = 4 	imes 3.14159 	imes 100 = 1256.6\, lumen$.Rounding to the nearest provided option,the correct value is $1256\, lumen$.

Effects	Reasons
$(i)$ Rainbow formation	$(a)$ Reflection
$(ii)$ Red colour of danger signals	$(b)$ Scattering
$(iii)$ Different colours of thin oil film and soap bubbles	$(c)$ Chromatic aberration
$(iv)$ Coloured images formed by lenses	$(d)$ Dispersion
$(v)$ Different colours of clouds	$(e)$ Interference

The maximum illumination on a screen at a distance of $2\, m$ from a lamp is $25\, lux.$ The value of total luminous flux emitted by the lamp is

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