For inquisitive minds only

[anthony_carlsberg]

Any of you ever wondered if the weights of negatives/transparencies

do change after exposure? Do they get lighter or heavier?

 

I realize that if they do it must be a miniscule amount but still I�d

like to know your thoughts on the subject :-)) AC

[pdumais]

No, but I suppose they would get a minuscropic trifling of a fraction heavier from the absorbed photons (conservation of energy/mass).

 

You would get a much bigger variation from develoment. And even that would be a very, very, small quantity. Not sure which way that would go. You'd have to check the chemical reaction.

[stephen hazelton]

They should not change weight at all after exposure. They should get lighter after development. And no, I never wondered that.

[j.w.]

Isn't the latent image a result of broken chemical bonds caused by photon bombardment? If bonds are broken, that means less binding energy, which implies less mass/energy equivalence in the molecule.

 

However, its not clear in my mind if the photon is absorbed or does it re-emit after breaking the bonds? If its absorbed, that may offset the energy loss from bond breaking; if its re-emited, then that implies a net loss for the molecule.

 

Or some such BS.

 

However, I suspect one could find a more measureable weight change after fixing, when undeveloped silver is removed from the emulsion.

[steve_baggett]

Joe, the latent image is not formed by breaking any chemical bonds in the emulsion. The photons are absorbed by the shared electron cloud in the silver halide crystals and, thus, change the electron clouds' quantum mechanical "state" a tiny amount. The state is "higher" in terms of electron energy levels, so it would have a miniscule greater mass (delta-energy divided by c-squared, giving a really tiny number). It is during development when chemical reactions take place, the rate of which varies according to how many crystals have been "altered" and to what degree. I like the question. Enquiring minds want to know.

[richard_cochran]

Photons have zero mass, so the emulsion won't gain mass due to

absorbed photons.

<p>

I believe the exposed silver grains are at a slightly higher

energy state, so mass would increase ever so slightly by

Einstein's E=mc**2 solved for m, or E/(c*c) = m.

But E is very small, and c-squared is

very large, so m would be really, really tiny.

You're not changing the number of protons, neutrons,

or electrons anywhere, just changing their energy

state ever so slightly.

<p>

The mass changes with temperature, too, if you want to get

way more precise than you can measure. Relativistic mass

increases with velocity, and average velocity increases

with temperature. Of course, exposure causes a slight

temperature rise, as the electromagnetic radiation is

absorbed by the film. This thermal energy absorption

at exposure may in fact be greater than the energy due

to the photochemical effect of exposure -- both are

way too tiny to measure.

<p>

I'm confident that, across a 35mm frame, the adsorption or

loss of a molecule or two of water from atmospheric humidity

would cause a much bigger mass change than any change that

happens due to energy changes from exposure.

<p>

This whole discussion reminds me of my physics professor

going through the calculations to figure the approximate

recoil force on a flashlight due to the momentum of the

expelled photons.

[skygzr]

The negative gets LIGHTER as it gets darker, because it absorbs dark light, which is emitted by dark matter (that�s why the negative turns black). Of course, shadows emit lots of dark light, which is why they�re bright on the negative. Anyway, dark light has a negative energy (mass), and so the mass of the negative decreases is it�s absorbed. Obviously this is where we get the name �negative�.

[john_kasaian1]

FWIW, I always defer these kinds of issues to http://britneyspears.ac/lasers.htm

[scott_killian1]

You people need women in your lives. Or alcohol. Perhaps both.

[frank_scheitrowsky1]

Did someone say photons have NO mass?

[pdumais]

The mass of a visible photon would be around 5 x 10-to-the-minus-36 kilograms.

That's WAY bigger than zero.

[stephen hazelton]

From some website: "A new limit on photon mass, less than 10-51 grams or 7 x 10-19 electron volts, has been established by an experiment in which light is aimed at a sensitive torsion balance; if light had mass, the rotating balance would suffer an additional tiny torque. This represents a 20-fold improvement over previous limits on photon mass.

 

Photon mass is expected to be zero by most physicists, but this is an assumption which must be checked experimentally. A nonzero mass would make trouble for special relativity, Maxwell's equations, and for Coulomb's inverse-square law for electrical attraction."

 

Note that light has momentum, but not mass.

[chad_jarvis1]

Ah, the timeless particle vs. wave debate...

[Sandeha Lynch]

re: "Ah, the timeless particle vs. wave debate..."

<p> Exactly - we need answers.

<p>And while anybody's at it, does over-exposure make a difference to the mass of the negative? Even if only by one or two stops?

[jonathan_brewer1]

Lorentz transformations notwithstanding, ............fat meat is always greasy.