[The Tao]

Here is the problem word for word:

"A sodium flame has a characteristic yellow color due to emissions of wavelength 589nm. What is the mass equivalence of one photon of this wavelength (1 J = 1kg*m^2/s^2)?"

Ok so I know the equation λ= h/mu, where h is plank's constant and u is the velocity of the particle. The question seemed simple enough but I realized that I don't know what u is.

And I also know the equation E= hv, and I can easily find out what v is by using c= v*λ, and so if I had E in joules, I thought it would be simple enough to perform some basic dimensional analysis on the unit J to get kg, but I just can't seem to get the answer.

Is it simpler than this?

The anwser is 3.75*10^(-36) Kg by the way.

[enahs]

It is easiest to work it with the only thing most people know about Einstein (though they have no clue what it means).

E=mc²

[The Tao]

Ah! Thank you very much that was quite simple indeed. I was going to use that equation but when I saw that E=mc^2 I thought that the units on the speed of light were m^2/s^2, and of course leaving an s on th matter, and thus being g/s, which didn't make much sense.

And about Einstein's equation... nobody understands it? Radiant energy (light) is given off when electrons fall to lower orbitals. If the electrons are emitting something traveling at the speed of light, and nothing can travel faster, would not then the total energy of the atom be governed by the limited factor of light?