what is the energy density 2.0m from a 100 W light bulb. light travels 3*10^8 m/s?

Answer 1

The surface area of a sphere 2m from a light bulb is 4(pi)r^2 or 16pi so dividing the 100W from the light bulb into the surface area we get about 100/(16pi) or approximately 2watts/meter. The speed of light is not important.