what happens to photons ?

[rory]

this is probably my first question ive ever asked about understanding physics(or whatever it may come under)

im interested to know what happens to the photons that have traveled millions of light years once they hit my eye ?

do i simply absorb them ?

as you can tell i never even managed a c.s.e in science's

[LeeB]

This is not aperfect answer but from memory tests have shown that a single photon reacts with a substance called rhodopsin in the rods of the retina its energy changes the molecule shape and a signal is sent along the optic nerve. However there is some filtering and it normally takes ten or so photon to trigger the impulse. Also as the eye absorbs 90% of the photon before they reach the retina 90-100 photons must enter the eye

[rory]

thanks, so we absorb its energy/mass in essence then ?

[Islander]

Photons are the gauge bosons or charge carriers for the electromagnetic force. When a photon hits an atom, it transfers its energy and causes the atom to switch to a higher energy state. The photon is absorbed by the atom. Energy cannot be created or lost.

[sanmatt]

2nd law of thermodynamics innit Islander?

Tell me I at least remember something from my degree?

[jimmyjamjoejoe]

Photons are constantly being absorbed/reemmitted by atoms in their paths towards our eye (and inside our eye).

As stated above, they cause a reaction in chemicals/cells in our eyes, but the energy is not then somehow funneled into our nervous system etc. It merely serves to trigger a reaction, much like a relay being triggered by a pulse. It is our body which then fires signals down the appropriate nerves etc.

[themos]

The energy is always being transferred between the electromagnetic field ( we call that situation "photons" ) and motion of charged particles ( we call that an electric "current" ). It is quite amazing that stars millions of light years away are making electrons in your body move. That's the miracle of a transparent universe.

[sanmatt]

I'm reading a fab book about electricity (and magnetism) btw. by Patricia Fara - An Entertainment for Angels - Electricity in the Enlightenment'.

[Islander]

2nd law of thermodynamics innit Islander?

Tell me I at least remember something from my degree?

You're thinking of the first law - it's a version of the conservation of energy. The second law is that entropy always increases (hot flows to cold, never vice versa).

[sanmatt]

You're thinking of the first law - it's a version of the conservation of energy. The second law is that entropy always increases (hot flows to cold, never vice versa).

No wonder I barely passed that module then!!

[rory]

thanks. youve all lost me ,but thanks.

[sanmatt]

Are you down the back of the sofa Rory??

[rory]

this is the side of astronomy i struggle with as a intellectually challenged type. maths, physics laws ect. i was reading the beano when i should have been studying.

im the guy who found the first chapter and a half of "a brief history of time " fascinating,from there on .

[sanmatt]

Me too. I just like to look at things, even though I dont understand a word of it

[themos]

We can always learn more in this hobby, no matter how much we already know.