Light intensity problem
Thomas has just bought a new light sensor, and he decided to test it out. He approached the very first light source he saw and meassured some intensity, then Thomas walked 20 more meters away from the light source and discovered that the light intensity was then 9 times less than initially, however, Thomas had forgotten to meassure his initial distance.
What was Thomas' original distance from the light source?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
From the given conditions of the problem, we have 9 p 2 = ( p + 2 0 ) 2 , or p=10, ( since p can not be negative) where p is the initial distance.