# Electromagnetic Waves

• Electromagnetic waves are transverse waves that include a wide spectrum of different types of waves including: radio waves, microwaves, infrared waves, visible light, ultraviolet waves, x rays, and gamma rays.
• These waves are grouped together into the Electromagnetic Spectrum based on their frequency and wavelength.
• All electromagnetic waves travel at the speed of light in a vacuum, which is approximately 3 x 10^8 m/s.
• The wavelength and frequency of an electromagnetic wave are inversely proportional. As the frequency increases, the wavelength decreases, and vice versa.
• These waves can travel through a vacuum, unlike sound waves which need a medium to travel through.
• All electromagnetic waves can transfer energy from one place to another and they all show wave properties such as refraction, diffraction and interference.

# Refraction

• Refraction is the bending of waves due to a change in speed when they pass from one medium to another.
• When a wave enters a more dense medium (like from air into glass), it slows down causing it to change direction and bend towards the normal line.
• Conversely, when a wave enters a less dense medium (like from glass into air), it speeds up and bends away from the normal.
• The angle of incidence and the angle of refraction are used to determine the amount of bending that will occur. These angles are measured from the normal line, not from the surface of the medium.
• When light passes from a less dense to more dense medium at a high angle of incidence (greater than the critical angle), it cannot pass into the new medium and is completely reflected back into the original medium. This is known as total internal reflection.
• Refraction has many uses in optics, including lens manufacturing and fibre optics, because it allows light to be focused and directed.