wavelength alteration

[lightoftruth]

Is it possible to lower and increase wavlengths within the electomagnetic spectrum. I.e lower light to microwves etc.

[fo3nix]

Yes. Wavelength is just a measure of the energy of the photons that comprise the light/x-rays, etc. So you can change their energies, and hence the wavelengths.

[gen2]

Molecules and atoms do it all the time. They absorb energy at one wavelength and re-emit it at another.

Another way is to move the source rapidly towards you (blue shift) or away from you (red shift).

[lightoftruth]

so if that is the case in solar power why dont they covert light to microwaves and heat the water that way.

[rojash]

The answer's in the bit "you can change their energies, and hence the wavelengths." You would need to add energy to change the light to microwaves, which would defeat the whole object of solar power (i.e using the (free) energy already in the light to create heat).

[jake-the-peg]

Ah hang on this isn't such a dumb idea.

A good example of frequency change is flourescence, UV light is absorbed by a material and retransmitted as visible light. Think - glowing white underwear at discos.

Now consider how a microwave oven works, it emits microwave energy at just the right frequency to excite water molecules.

Conceivably you could have a material that absorbs light and retransmits at the resonant frequency of water.

However that's a pretty specific frequency and would require a rather special material which might or might not be feasible

[heathfield]

The simplest means at present would be to use photo-voltaic solar panels to power a device that generates whatever part of the electromagnetic spectrum you require.

[Space]

No, photovoltaic cells powering something wouldn't be the simplest solution. And it would waste a lot of energy, because photovoltaic cells have a very low efficiency.
A solar water heating panel would be more simple and more efficient.

You don't need microwaves to heat up water. Sunlight can do it too. Some solar panels are made specifically for water heating, and they are much higher efficiency than phtovoltaic cells.

[heathfield]

Space - sorry, but I thought we were talking about a shift to any part of the electromagnetic spectrum. If so, my answer stands.

[lightoftruth]

I always thought that microwaves were more effecient as heating water because it takes less time than leaving out in the open.
Basically if a material was found could i effectivly harness the microves and focus them on to a particular point ie a boiler.

Also what i was thinking is that for instance lets say with have gamma rays for 1 metre. if that were converted into light it would go a lot further so their would be more of it. So their would be more potential microwave in light than their is in a microwave itself.

[jake-the-peg]

It's not that microwaves are more efficient, rather that one specific frequency of microwaves is more efficient.

This is the resonant frequency of water a little higher frequency or a little lower and you lose the heating effect.

If cou could convert incident light to that microwave frequency you could have a very efficient way of heating water. Of course you'd have to coat it with a material that transmits light but reflects microwaves to get the best effect.

I don't understand quite what you mean about gamma rays "going further" gamma rays are very very higfh frequency photons they still travel at the speed of light just like radio waves or ultra-violet etc. It's just that the energy of a photon is proportional to the frequency so a gamma ray photon has a lot of energy. Of course gamma rays are mostly blocked out by the atmosphere.

However if you could fing a material that flouressed at 2450Mhz you could make a cup out of it and coat it with another appropriate material you could put cold water in it and it would heat up in daylight.

However the fact that nobody has done this yet makes me think it's not easy/possible

[Gef]

rojash, visible light is of higher energy (lower wavelength) than microwaves.