A spherically spreading EM wave comes from a 1400-W source. Assume that the wave travels in free space. What is the intensity at a distance of 4.2 m ? Express your answer using two significant figures.

Given Information:  

Power of EM source = W = 1400 Watts

distance = d = 4.2 m  

Required Information:  

Intensity of Radiation = I = ?  

Intensity of Radiation = 6.31 W/m²

Explanation:  

The intensity of the electromagnetic radiation is the energy delivered by the photons.

Electromagnetic radiation are of many types including Gamma rays, X-rays, Ultraviolet rays, Visible light, Infrared, Microwave, and Radio waves.

The intensity of a spherically spreading electromagnetic radiation is given by  

I = W/4πd²  

Where W is the power of the EM source and d is the distance from the center of the EM source.

So the Intensity of radiation is

I = W/(4πd²)  

I = 1400/(4π(4.2)²)

I = 6.31 W/m²

d) physical means can be used to separate the components of air.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach