What are the units of the energy of a photon and the energy of light? I know light intensity is the number of photons that corresponds with the wavelength so from the information I would guess the unit would be number of waves per second.

Question

anonymous · Answer

Energy of a photon=hv
h=Planck constant. Its units are J*s or joules times seconds
v=frequency. Its units are 1/s
Energy of a light is energy of photon, since photon is a packet of light.
Do you mean speed of light?

dessyj1 · Answer

I understand now. I was never given the units to Planck's constant. I was just give a number.

anonymous · Answer

The question is just asking for units

Planck constant is 6.626 x 10^-24 J*s btw

dessyj1 · Answer

Yeah, i was not shown the j*s - i was only shown the number. So when i would do calculations with planck's number the units would not cancel completely because i did not know the j*s.

anonymous · Answer

You do not need numbers to figure out the units.
I give you explanation, but not the answer. (I know the answer)
You can figure the answer by my info.

Example problem:
Velocity=distance/time
Units of distance=m
Time=s
Velocities units would be m/s

Just wondering if you can figure it out.

photon336 · Answer

$$E = hv $$

$$E = \frac{ hc }{ \lambda }$$

dessyj1 · Answer

I understand what you are saying. I did not know the units for planck's constant so when I would try a practice problem like this one, it would go like this. 

What is the energy of a photon of green light with a 520nm wavelength?

$$E _{p}= \frac{ hc }{ \lambda } $$
$$E _{p}= (6.626x10^{-34})(2.998x10^{17}nm/s)(\frac{1}{ 520nm })$$
so, at the end of the day I would be left with a unit of 1/s(which did not make sense to me) because I did not know the full mangitude of planck's.

anonymous · Answer

Do you know the units for the energy of a photon now?
If you do, then I can continue to solving problems with you.

dessyj1 · Answer

Yes, it is in joules.

dessyj1 · Answer

If I modified the question and said there were 10 photons in the wave, what would be the answer.

dessyj1 · Answer

Are photons measured in mols?

anonymous · Answer

You are right.
It is in joules.
Modify which question?

dessyj1 · Answer

What is the overall energy of  green light with a 520nm wavelength that contains 10 photons?

anonymous · Answer

You would multiply it by 10 since ten more photons means then more energy.
E=hv/wavelength only applies to one photon

anonymous · Answer

ten more energy*

dessyj1 · Answer

would the units still be just joules?

anonymous · Answer

Yes.
Lets say a photon has an energy of 500J
10(500J)=5000J

dessyj1 · Answer

Okay. Thank you!

dessyj1 · Answer

How would you measure photons?

dessyj1 · Answer

Or is it very discrete?