## Calculating the number of photons [ENDORSED]

Posts: 72
Joined: Wed Sep 18, 2019 12:18 am

### Calculating the number of photons

How do you calculate the number of photons as described in 1B.9? Is it just another way of asking to find the amount of energy? I'm confused. Thank you :)

MinuChoi
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

### Re: Calculating the number of photons  [ENDORSED]

You can use the equation E=hv, which refers to the energy of a single photon of light.

In this problem, you're asked how many photons have a total given amount of energy. You're given the wavelength of the photons, so you can convert to frequency, use E=hv to find the joules per photon (E), and then divide your energy amount by E (in this problem, 32J/s x 2.0s = 64J) to get the number of photons that would have that total of energy.

Baoying Li 1B
Posts: 113
Joined: Sat Aug 17, 2019 12:18 am

### Re: Calculating the number of photons

First, you need to find the velocity of a proton by using the formula v=c/wavelength. Then you can find the amount of energy per proton by using the formula E=hv. You use the total energy in the 2s divide by the energy of one proton. You will get the total amount of protons in this energy. In order to find how many moles of photos, you will use the Avogadro's constant to convert photons to moles. Hope this helps.