## Sapling Week 2-4 Homework Question #4

$c=\lambda v$

Mrudula Akkinepally
Posts: 115
Joined: Wed Sep 30, 2020 9:31 pm

### Sapling Week 2-4 Homework Question #4

I'm stuck on this problem and I was hoping I could get some of your help!

So the question asks how many photons are required for the liquid to absorb 30.59 J of heat. I started by finding the energy of the photon and ended up with 3.49 x 10^-24 J. I then divided 30.59 J by 3.49 x 10^-24 J and ended up with 8.77 x 10^24. However that was wrong. When I flipped it and did 3.49 x 10^-24 J divided by 30.59 J, I got 1.14 x 10^-25, which was also wrong.

I read the feedback on sapling and my process is correct but maybe my numbers are off? Please let me know!

Annie Tong 2G
Posts: 51
Joined: Wed Sep 30, 2020 9:42 pm
Been upvoted: 1 time

### Re: Sapling Week 2-4 Homework Question #4

Hi! (So first this is question #5 by the way :) )

I found the energy of the photon by settling E = hc/λ and got 2.486 x 10^-20 J so I think your numbers were a bit off. Then you can divide 37.79 J by 2.486 x 10^-20 J to get the number of photons needed.

Hailey Kang 2K
Posts: 115
Joined: Wed Sep 30, 2020 10:03 pm
Been upvoted: 1 time

### Re: Sapling Week 2-4 Homework Question #4

Hello! The first thing you need to do is solve for the energy of one photon, which you can do through the equation E=hc/λ. After that, you divide the given energy by the one that you found and that should give you the correct answer. I think everybody's numbers are different but I can attach my work below just so you can see the steps I did. Hope this helps!

Mrudula Akkinepally
Posts: 115
Joined: Wed Sep 30, 2020 9:31 pm

### Re: Sapling Week 2-4 Homework Question #4

Thank you for your responses! I realized that my error was in my conversion from cm to m. It was a very simple error but it threw off my whole calculation!