HW 1B9

[Jason Wu 1E]

A Lamp Rated at 32W (1W=Js^-1) emits violet light of wavelength 420 nm, how many photons of violet light can the lamp generate in 2 seconds? How many moles of photons were emitted in 2 seconds?

For this question, I first calculated how much energy is released by a single photon through using
. However, how do you relate this value (in Joules) to the number of photons released? As for moles of photons is the conversion still 1 mole of photons = 6.022* 10^23 photons?

[Angus Wu_4G]

We are given the fact that the lamp is shined for 2 seconds, and the light is a 32W light. Therefore, in those 2 seconds, the lamp emitted 64 joules of energy.

By using the E=(hc)/(wavelength) equation you found the energy released by a single photon. Essentially, now you just have to find how many of those photons you need to be equal to 64 joules.

And to answer your last question, yes, a mole of photons is still 6.022x10^23 photons.

[Jared Khoo 1G]

You would want to take 32W * 2 seconds and divide it by your result from the energy released by each photon. You then should take the photons you have and divide by 6.022 *10^23 photons/mol, leaving you with moles of photons.