A 60-W light bulb radiates electromagnetic waves uniformly in all directions. At a distance of 1.0 mfrom the bulb, the light intensity is I0, the average energy density of the waves is u0, and the rms electric and magnetic field values are E0 and B0, respectively. At 2.0 m from the bulb, what is the light intensity?

I0/4

Explanation:

If the difference is increasedby a factor of two(i.e twice it's original value), then the light intensity happens to get reduced by one-fourth. This means that the light intensity would be:

I0/4

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

i really dont know but i will try okay.

so i think u would just add all them up and get your answer..