camerono
Sep 7, 2008, 05:20 AM
I am studying variations (direct, inverse, joint)
Given: the intensity of light, measured in lux, is inversely proportional to the square of the distance between the light source and the object illuminated - solve:
A light meter 7.5 m from a light source register 24 lux. What intensity would it register 15 m from the light source?
I tired to use the inverse variation equation y=k/x.
I thought that y would be 24. And x would be the square of the distance 7.5
24=k/56.25
so 1350=k.
substituting:
24=1350/225 (15x15)
24=6
obviously this is incorrect. Can someone guide me as to what formula I should be using? I have spent a long time rereading the section in my text but I just don't get it. Thanks.
Given: the intensity of light, measured in lux, is inversely proportional to the square of the distance between the light source and the object illuminated - solve:
A light meter 7.5 m from a light source register 24 lux. What intensity would it register 15 m from the light source?
I tired to use the inverse variation equation y=k/x.
I thought that y would be 24. And x would be the square of the distance 7.5
24=k/56.25
so 1350=k.
substituting:
24=1350/225 (15x15)
24=6
obviously this is incorrect. Can someone guide me as to what formula I should be using? I have spent a long time rereading the section in my text but I just don't get it. Thanks.