Laser Light

[wikidrox]

I do not know how to do the second part of this question. I never learned this.

A laser used to weld detached retinas puts out pulses of 640 nm light, 25 ms long, which average 0.50 W output during a pulse.
i) how much energy can be deposited pre pulse?
ii) If the energy of a light particle (photon) is about 3 * 10^-19 J, how many photons does each pulse contain?

I do not know how to get this.

[swansont]

I do not know how to do the second part of this question. I never learned this.

A laser used to weld detached retinas puts out pulses of 640 nm light, 25 ms long, which average 0.50 W output during a pulse.
i) how much energy can be deposited pre pulse?
ii) If the energy of a light particle (photon) is about 3 * 10^-19 J, how many photons does each pulse contain?

I do not know how to get this.

If you have the energy from the first part (E=Pt), and you know how much energy is in each photon, you just have to figure out how many photons give you that energy.

Etotal=N * Ephoton