How light behaves
Wavelength and frequency affect the way light interacts with different materials
Transmission
Transparent objects allow light to pass straight through without absorbing much of its energy. When light hits the object’s electrons, they vibrate a little before re-emitting the light in the same direction. The energy passes from atom to atom and out through the other side.
Reflection
Reflective objects bounce light back. When light hits, the electrons vibrate but they don’t absorb the energy. Instead, they send the light out towards neighbouring atoms. The angle of reflection is equal to the angle at which the light hits the object, which is known as the angle of incidence.
Absorption
Opaque objects absorb light, converting its energy into heat. This happens when the frequency of light matches the frequency of the vibrations of the object’s electrons. Colourful objects absorb some wavelengths and reflect others, changing the composition of the light that we see.
Refraction
If light passes from one material to another at an angle of 90 degrees, nothing special happens. However, if the materials have different densities and the angle is off, the light will refract. Different parts of the wave hit the boundary at different times, causing the light to change direction.
Diffraction
When light passes through a gap smaller than its wavelength or passes a particle of a similar size, it diffracts. As the waves pass through the gap they bend and spread out. The smaller the gap compared to the size of the wavelength, the more the light diffracts.
Scatter
Electrons don’t always re-emit light in a set direction; instead of transmitting or reflecting the waves, they send the energy out at a random angle, causing scattering. The amount of scattering depends on the type of atom and the frequency and wavelength of the light.