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Optics

Optics is an area of physics which looks at how light behaves and how we can observe it. 

This usually involves using mirrors and lenses to magnify, focus, and direct the path of light.

An everyday example of this is the use of corrective lenses in glasses which improve people's sight. The lenses change the focal length of the light. The focal length is the distance from the centre of the lens to the focus point of the light. 

This allows the wearer to see a focused image instead of a blurry one.

 

There is an illustration of a bulging lens on the left. A dashed line runs through the centre across the image. Two red parallel lines hit the lens towards the top and bottom and then become diagonal, crossing paths at a point labelled "F" some distance after the lens. This distance is noted with a black arrow labelled "f'".
This work by JiPaul (based on work by Henrik) is licensed under Creative Commons Attribution Share Alike 4.0 International
Light (red lines) passing through a convex lens. The point at which the light meets (F') is called the focus. The distance from the lens to the focus (f') is called the focal length.

The main use of optics in astronomy is in telescopes. Telescopes use lenses or mirrors to magnify the light coming from distant objects in the Universe. This lets us see fainter objects, and lets us see more detail in the image. 

We also use lenses and mirrors to focus the light. This lets us look through the telescope with a camera and collect get data from the observations. Instruments called interferometers combine the light collected from 2 or more telescopes.

A ray diagram shows the path light takes as it travels. It includes what happens when it reaches a surface, such as a lens or a mirror. The direction and angle light travels through a telescope will vary depending on design of the telescope.

Part of
Telescope Design
Telescopes
Telescope
Light