Thread: changing light frequency

is it possible to change the frequency of light?
for example, the earth gets visible light in high intensity but since its freq. is low, it cannot be used fro photoelectric effect etc. so, wthout changing the total energy, is its possible to convert the light into 2 parts: 1 low freq. infrared and the other high freq. UV?
and what is the raman effect?

Originally Posted by saaz

is it possible to change the frequency of light?
for example, the earth gets visible light in high intensity but since its freq. is low, it cannot be used fro photoelectric effect etc. so, wthout changing the total energy, is its possible to convert the light into 2 parts: 1 low freq. infrared and the other high freq. UV?
and what is the raman effect?

Visible light is already a mix of different frequencies of light between 4.3e14 - 7.5e14 hz.

You can separate these frequencies with a prism (this is what a rainbow is) , but you can't get any higher or lower frequencies than are already there.

The Raman effect is when a photon interacts with a the electron cloud of an atom. The photon excites an electron into a higher state, and when the electron returns to a lower state it emits a photon. Depending on conditions, sometimes the photon is the same frequency as the original, sometimes lower, and on rare conditions, Higher. (for higher, the electron would have to already been in an excited state.)

Fluorescent lights use a form of the Raman effect. The gas inside the light gives off ultraviolet light, which interacts with the coating on the inside of the glass envelope. Electrons in the coating are excited and then fall back to base levels in steps emitting lower, visible light range photons.

There are instances where two photons of the same energy can get added together into a new photon of twice the energy. I don't know much about this or how it works though. I think it has something to do with the material the photons were passing through.

Originally Posted by saaz

is it possible to change the frequency of light?
for example, the earth gets visible light in high intensity but since its freq. is low, it cannot be used fro photoelectric effect etc. so, wthout changing the total energy, is its possible to convert the light into 2 parts: 1 low freq. infrared and the other high freq. UV?
and what is the raman effect?

frequency division can be done.. but at that high frequency, i am not sure. wave effect on material is different on this stage. i doubt if magnetrons and wave guides would work to do the frequency division.
and i think you'll need to spend energy on this.

As the other guy said, white light is composed of a spectrum of light already.

Just filter the ones you need.

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Janus

Originally Posted by MagiMaster

There are instances where two photons of the same energy can get added together into a new photon of twice the energy. I don't know much about this or how it works though. I think it has something to do with the material the photons were passing through.

This is correct, u can make a material where above the ground state there are two energy states which are both seperated by a given energy E. If a photon of energy E comes in and excites an electron into the first energy state, and then, BEFORE the electron decays, another photon of energy E can be absorbed, the electron will be excited again into the second excited state. The materials electronic state can then radiatively or non radiatively (or a mixture of both) relax. If the relaxation mechanism is a complete radiative relaxation (back to the ground state), a photon of 2E is released.

This is called up-conversion. People look at using these materials for many applications such as for solar conversion ( placing them on top of a solar cell designed to be optimal efficiency at the 2E energy ), or for heads up displays.