Optics

Light

Light is made of electromagnetic radiation, a form of energy. "Light" usually refers to visible light, the sort that we can see with the naked eye.

One of the defining properties of light is its wavelength. In visible light, this property defines the colour it appears to be. However, light also exists with many other wavelenghts, beyond that which we can see.

Lenses

When light passes through something transparent, it changes direction by a small amount. The amount of change of direction depends on the substance. This effect is called refraction.

Different colours of light, because they have different wavelengths, will refract at slightly different angles. This is how a prism works. White light is composed of many different wavelengths blended together. When the light passes through the prism, its different components refract at slightly different angles. When the light leaves the prism, it has been visibly separated into its component colours.

When light passes through a surface that is not flat, the refracting light will not all travel in the same direction.

Refraction happens exactly at the surface between the air and the lens. When light passes all the way through the lens, it changes direction at both surfaces.

Mirrors

A mirror is anything which that reflects light in a way that it can form an image - anything that "makes a reflection." Most of the light that hits a mirror is bounced back off, in a way that keeps the image intact.

Most of the mirrors we use for everyday use are flat, and create an image which appears to be the same size as the original. When mirrors are different shapes, the images appear different sizes or different shapes. A concave mirror causes the light reflected from it to be directed inwards, towards a focal point.