Eye: The Human Video Camera

Eye spy with my crooked eye!

There are too much fascinating things about our own body it's unbelievable. Our pair of eyes is probably the most compelling, as I couldn't imagine my world of science without them so I take real care for mine (I assume you do too, or I will be more than happy to withdraw your eyes out and donate them to someone else who may have better use for them, and I'm not joking we're that lucky to have them)(!). It's one of our more delicate organs - at the same time being our most useful and unique. It can detect single photons dashing around (light for non-physicists) and it will convert these energetic wave/particles into electro-chemical impulses allowing us to see. They work at a specific rate which makes us humans see a certain amount of 'views' each second, this rate is so high that it seems smooth to us, hence it's related to a video camera working in the same process. I also relate the eye to a video camera because in our mind we can 'playback what we recorded'. We have the ability to look at something, close our eyes and picture the same image in our heads and we it helps us to recognise familiar faces in pictures. Invertebrate animals' eyes are slightly different from vertebrates because it may be adapted to view object in a certain angle, or underwater etc. But they work the same, so it's fine.

Reading this with my subsequent blogs you should realise this is probably the odd one out so far: this is a biology topic (cheesy). But eyes are that fascinating that I'm going to approve this onto my blog by calling it a biophysics topic (since it's the physics of the eye I'm really interested in). But at the same time I think you should know the basics about it, and below is a diagram that shows the main components of the eye which together collaborate to make the eye successful. If something went wrong with one of the components, the eye make stop functioning.

The lens is one of the more-know parts, is there to help focus light output into the retina. Dioptres is what is used to measure the curvature of an item and the lens contributes to roughly a third (18) of the total curvature produced by the eye. Cataracts is known as the opacities (reduced transparency) of the lens which blocks light going through and eventually reduces sight. Muscles in the lens contract and relax simultaneously to preform a function called accommodation which is the switching of focusing on the lens from short sighted/close up vision to long sighted/long-ranged vision, and it's a reflex. Many people wear glasses because one of the type of visions does not focus properly, and the glasses they wear have lens in shape according to whether they're long sighted or short.

The Iris controls the amount of light entering the eye, depending on the intensity of light in the surroundings. In dark areas the iris widens to allow more light to go through inside the eye so we can see more things. Cat like animals are known for having very adaptable irises. The colour of the iris is one of the main genes learnt in school that are inherited from parents, where brown irises are the dominant colour (no I do not know why, but you can find biologist to help you answer this question using your own eyes).

The cornea is the transparent film around the eye which you touch if you want to poke the eye, and does most of the contribution to refracting light into the eye (the other two-thirds infact). The pupil acts as the next shield up which absorbs all the light through its tissues (which explains why it appears black).

The retina is the 'conversion' part of the eye. Here lies the mechanical processes inside the eye, as this is where all the light is converted into impulses sent to the brain. The retina also does basic optical processing, such as edge detection and colour separation. So ultimately, it produces the image that we see.

That's pretty much the basics about the eye (all you'd need to know if you happen to be in a quiz night, and they ask you questions about the eye anyway), but I can tell you a cool error called aliasing. Aliasing happens when you see something move, but it's moving faster than the enumerated images your eyes record every second, so the view of what you see moving fast actually looks like it's going slowly, or irregular movements. Aliasing is also produced when you infrequently sample a piece of analogue signals in music - the coded samples join together to produce a completely different signal. Here's a video that demonstrates what I'm blabbing about: