Question: Hi Alex I was wondering if you could explain how eyes see light thankyou

Alex Agrotis answered on 23 Apr 2020:

Hi rorymac888!
The main parts of the eye are the cornea (clear front surface), iris (coloured part with pupil/hole in the middle), lens (this is behind the iris) and retina (back of the eye).
Light enters the eye passing through the cornea and pupil. The iris is able to change the size of the pupil to control the amount of light entering the eye, so in the dark the pupil is large to let in more light.
The lens (which you can’t see) is controlled by muscles which change its shape to focus the light. To focus on something close, the lens needs to become ‘fatter’.
Finally the light passes through the liquid inside the eyeball and reaches the retina, which contains special nerve cells called ‘photoreceptors’. These send messages to the brain when they are activated by light, and your brain converts these signals into an image. Your brain also fills in a lot of gaps in information to build up a picture of the world around you.
There are two types of photoreceptor – rods and cones. Rods are more sensitive to dim light, but cones can detect colour. Cone cells are mainly found in the most sensitive part of the retina – the fovea – which detects the centre of our vision.

You can read more about rods and cones here:
https://faculty.washington.edu/chudler/retina.html

Here’s a page that has a nice diagram of an eye:

How do our eyes work?