In the first part of our blog series we will talk about what the light is and where it arises and how it gets to our eyes.
Imagine yourself sitting at your garden on a sunny summer day. Clear blue sky and a delightful warmth coming from the Sun. Sounds familiar, right? It was about a ten thousand years ago, when people were still living in caves and first civilizations were just starting to form, when the first process, that enables you to see at this very moment, took place. It was back then when deep inside the Sun the light you see now was born. Eight minutes ago, it finally got to the surface of the Sun and now it is here, at your garden. Yes, it took it ten thousand years to get from the core to the surface of the Sun and only 8 minutes to cover a hundred-million-mile journey between the Sun and the Earth.
On its way, however, important processes took place. The light, or shall we say radiation, that comes from the Sun is toxic for humans and as such it could kill us instantly. Without any protection it would be like standing next to a nuclear reactor or an X-ray machine. In other words, deadly. However, our Earth gave as the protection we need. The magnetic field and the atmosphere protect us from virtually all harmful radiation that derives from the Sun. What it does reach us, however, is a little bit of ultraviolet (UV) light that enables us to make some vitamin D and get some tan, the visible light that enables us to see and a lot of infrared (IR) light that we perceive as warmth. Still following? Yes, the visible light or what we think of when we say the light is only a small part of the radiation that derives from the Sun. Such a small fraction and yet so important for us all. Contrary to some animals, humans are only able to perceive light with a rather narrow spectrum, with the wavelengths between 400 and 700 nm. Why is it so? It has all to do with the retina and the photoreceptors which we will cover in some later blogs.
Anyway, you now know how the light is formed and how it gets to your eyes. Want to now more? Stay tuned as in the next blog we will explain what cornea is and what important function for vision it has got!
P.S. Do not be confused with the fact that we were only talking about the light that derives from the Sun. We obviously know a lot of artificial sources of light (fire, light bulbs, light-emitting diodes, etc), that make our lives so much easier.
N.B. UV light is harmful to your eyes as well as your skin. Avoid excessive UV exposure!
Missed few parts of the series? Check them out:
Part III: Iris, pupil and lens
Part IV: Refraction and the Eye Globe
Part V: The retina (and the vitreous)