In: Physics
How quickly does the flux of light from an isotropic source if, decrease with distance r? For a perfectly collimated source, the flux does not decrease as one moves away from the source (as long as one stays within the beam). You have at your disposal two sources: an isotropic source and a collimated source. At a distance of 1 cm from the source, the flux from the isotropic source is one hundred times brighter. Which source is brighter fifty centimeters away? At what distance from the source arc the two equally bright?
Light flux or Brightness can be calculated by using intensity formula.
The solution is following in pictures....