Alejandro L. answered • 10/26/16

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Dear Psalm,

I must start by saying that your instructor doesn't understand what it is that he/she is teaching because light has no mass and much less weight. I presume that the misunderstanding of what Einstein's equation predicts is the reason for this kind of question.

Technically, E = mc^2 only applies to mass particles, but for the sake of this problem we'll pretend that it applies. However, I do want to make sure that you understand this calculation is completely meaningless and has no physical truth to it whatsoever.

First determine the energy of orange light using Planck's equation:

E = hc/L

now substitute into Einstein's equation:

mc^2 = hc/L

solve for m:

m = h/cL = [(6.626x10^-34 Kgm^2/s)/(2.998x10^8 m/s)(5.90x10^-7 m)] = 3.75x10^-36 kg or 3.75x10^-24 ng

Once again, this is the answer to your question using completely misunderstood equations.

Alejandro L.

Since the wavelength only has 3 significant figures and all the other constants have four or more, I would stick with only three sig. figs for the final answer.

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10/27/16

Psalm H.

10/26/16