Light Unit: Moles

Ok, the story behind this is long and unimportant. Basically, there is an experiment involving plants, and measuring the light and temperature, only in this experiment, the guys used moles as the unit for light.
Now I have only ever used this in chemistry, so it has me completely baffled.

Does anyone know anything about this, what the unit is, what it is equivalent to, etc.

Reply 1

teachercol

Nope - never seen it used this way.

Candelas
Lumens
Candlepower

But not moles.

Reply 2

Wangers

moles as a analogy ti represent the numbers of photons perphaps?

Reply 3

teachercol

Seems unlikely for an experiment though.

I've been trying to think what its a typo for!

Reply 4

BibbleJW

Nope, found out now. 1 mole is 6.02 x 10^23 photons.
Bizarre way of doing it, I know, but that is what is used when dealing with Photosynthetically Active Radiation, apparently

Reply 5

Theorist

Isn't it one mole is 6.02 x 10^{23} atoms?

How do you measure one mole of light?

Reply 6

Wangers

OP - do you know if that was published in a reputable journal? Ie not the likes of NS, something of the ilk of Nature for example?(its just that its highly irregular) - Ie it directly contridicts the scientific conventions on the definition of moles.

Reply 7

vVPiKaVv

Wangers, I'm not exactly sure about the true definition of moles, but I did learn that 1 mole of photons = 6.02 x 10^23 photons too..

Reply 8

teachercol

A mole of photons is clear enough - but how do you count them?

Reply 9

Wangers

Well one group has been able to detect a single photon repeatedly within vacumne box system by using changes in magnetic fields due to quantum effects....I think the easiest way would be to backwards calculate it from known values - such as intensity etc.

Reply 10

teachercol

Quite - so measure in some other unit

Reply 11

BibbleJW

I think the idea was to only give out a certain frequency of light, and then measure the energy or something. I think plants only use 2 frequencies of light, anyway.

Reply 12

teachercol

I understand what youre getting at - but the reality is that we cant measure numbers of photons without measuring energy and then calculating. That's why our units for light intensity are in terms of energy not in terms of photons.

Reply 13

Morbo

I think it makes sense to use number of photons if you are considering photosynthesis - I'm not a biologist, but for example one photon may energise one chorophyll molecule to catalyse glucose production.

Hence, the number of glucose molecules produced will be a function of the number of photons absorbed.