Electromagnetic WavesElectromagnetic Waves

Electromagnetic waves are transverse waves comprising of electric and magnetic fields oscillating at right angles to each other. Different types of EM waves are classified by wavelength.

Type of EM wave	Wavelength
Radio waves	$> 10_{6}-10_{-1}$
Microwaves	$10_{-1}-10_{-3}$
Infrared	$10_{-3}-7times 10_{-3}$
Visible	$7times 10_{-7}-4times10_{-7}$
Ultraviolet	$4 times 10_{-7}-10_{-8}$
X-rays	$10_{-8}-10_{-13}$
Gamma rays	$10_{-13}-< 10_{-16}$

Note: there is some overlap between X-rays and gamma rays at wavelengths 10^-10 and 10^-13. Here, waves are classified by their origin: X-rays are emitted by fast-moving electrons, whereas gamma rays come from unstable atomic nuclei.

Refractive index: this is the ratio of the speed of light through a vacuum to the speed of light through a material. It is calculated by the equation:

$n =frac{c}{v}$

Refraction law:

nsin Theta =k

$n_{1}sin Theta _{1}=n_{2}sin Theta _{2}$

Total internal reflection is a phenomenon that occurs when light is travelling through a medium with a higher refractive index as it strikes the boundary with a medium with a lower refractive index. It occurs when the angle of incidence is greater than the critical angle.

$sinC = frac{1}{n}$

Technique and procedures used to investigate refraction and total internal reflection of light include ray boxes and transparent rectangular and semi-circular blocks. Semi-circular blocks are used to investigate TIR because the light enters the block at 90° to the boundary so does not change direction, meaning the critical angle can be measured accurately.