Intensity and Electromagnetic Waves (such a sensible combination i know)

what is intensity?

the radiant power passing through a surface per unit area. it has units of Wm^-2

what is the equation for intensity

I= P/A or I = P/(4*pi*r²)

for a point source of a wave….

energy and power spread uniformly in all directions, over the surface of a sphere

why is intensity directly proportional to amplitude²

• when the amplitude is halved, particles oscillate at half the speed

• when the speed is halved, the kinetic energy is quartered because E=0.5mv²

• intensity=power/area = (energy/time)/area so when energy is quartered, power is quartered and intensity is quartered

• therefore because ¼ = (1/2)² intensity is directly proportional to amplitude squared

electromagnetic waves and their vibes

• they do not need a medium

• only type of wave that can travel through a vacuum

• transverse

• electric fields and magnetic fields oscillating at right angles to each other

• can be polarised, reflected, refracted and diffracted

• travel at 3×10⁸m in a vacuum

what is the wavelength of radio waves?

10^-1 to 10⁶+m

what is the wavelength of microwaves

10^-3 to 10^-1m

what is the wavelength of infrared

10^-3 to 7*10^-7m

what is the wavelength of visible light

7×10^-7 to 4×10^-7m

what is the wavelength of ultraviolet

4×10^-7 to 10^-8m

what is the wavelength of x-rays

10^-8 to 10^-13m

what is the wavelength of gamma rays

10^-10 to less than 10^-16m