## 1B.9

$\lambda=\frac{h}{p}$

Posts: 55
Joined: Fri Sep 28, 2018 12:26 am

### 1B.9

A lamp is rated at 32W emits violet light of wavelength 420nm. How many photons of violet light can the lamp generate in 2.0s? How many moles of photons are emitted in that time interval?
How do you find the amount of moles using Watts?

Jessica Helfond 2F
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Re: 1B.9

Watts is equivalent to Joules per second. So in this problem, 32 W=32J/s. Then you can find the amount of photons the lamp generates, and then convert the photons to moles by using Avogadro's constant. Hope this helped!

Rachel Yoo 1F
Posts: 65
Joined: Fri Sep 28, 2018 12:24 am

### Re: 1B.9

Use the 32J/s to find the total amount of J in 2 seconds. Then use the equation E=(hc)/lambda to find the energy of one photon. With this you should be able to find the number of photons of a violet light. Then you can find the number of moles of photons by using Avogadro's number

Nina Do 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:27 am

### Re: 1B.9

A watt is also J/seconds so you can multiply 32 by 2 to get the total energy, 64 J. Then, use E=(hc)/lambda which will give you the energy of only 1 photon. I believe you then multiply the energy of 1 photon. You can then proceed to use 6.022*10^23 (Avogadro's) to find the number of moles.