Question 1056462
[ illumination ] = k*[ 1/distance squared ]
{{{ 15 = k*( 1/ 20^2 ) }}}
( note that {{{ k }}} is the constant of proportionality )
{{{ 15 = k*( 1/400 ) }}}
{{{ k = 6000 }}}
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given:
{{{ d = 50 }}} ft
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Let {{{ x }}} = illumination in foot-candles
{{{ x = k*( 1/50^2 ) }}}
{{{ x = k*( 1/2500 ) }}}
{{{ x = 6000*( 1/2500 ) }}}
{{{ x = 2.4 }}}
2.4 footcandles at 50 ft
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I can plot illumination on the vertical axis and
distance on the horizontal axis:
{{{ graph( 600, 400, -7, 70, -3, 30, 6000*( 1/x^2 ) ) }}}