The intensity of light at a distance 'r' from the axis of a long cylindrical source is inversely proportional to 'r'

Explanation

True. Intensity of light on a surface is the energy falling per second normally on unit area of the surface. The energy falling `//`second depends on energy density and the velocity of wave. Energy density on energy density and the velocity of wave. Energy density is the total energy per unit surface are. As we move away from the cylindrical source of light, the surface area `prop`r (the distance from axis)
`:.` Energy density `prop(1)/(r)`
`:.` Energy falling`//` second normally on unit area `prop (1)/(r)`
`:.` Intensity `prop (1)/(r)`