Frequency of Light and our eyes

[IB Andy]

This is just a question that suddenly pop into my mind.

Imaging that there are two different frequency of light flashing, what is the mechanism behind it to allow people to figure out which one goes faster? Is it because of the rod cells?

[Sandwich]

Cone cells (they detect colour). Rods detect only light intensity (and are actually totally inactive during daylight as the pigment is bleached out). It's a complicated system but effectively it works by having 3 groups of cones tuned into 3 main sections of light which are then activated by the wavelength falling on them and then act in a network (via other cells) to either upregulate or downregulate each other (inhibition vs activation, effectively). The net effect is seeing all the pretty colours :B

It's really complicated. There are many different interactions - for instance seeing one colour can repress your ability to see another colour, having light fall on the outer part of a receptor instead of the centre can cause reciprocal inhibitions/activations between cells next to each other in order to enhance outline definition and so on. Buy a book on Neuroscience/the Nervous System for the best explanations of the eye ((this one is excellent at explaining the eye), but only if you're really fascinated, ahah. You do have be quite fascinated!

You have to remember that wavelength (frequency) = colour, to us.

The actual frequency of lights flashing on/off and generally interpreting the inputs coming from the optic nerves and back to the brain all happens in the occipital lobe.

[IB Andy]

thank you, that really helps