## Sapling Week 2,3,4 #12

nayha a 1E
Posts: 63
Joined: Wed Sep 30, 2020 9:54 pm

### Sapling Week 2,3,4 #12

Calculate the wavelength, in nanometers, of the spectral line produced when an electron in a hydrogen atom undergoes the transition from the energy level n=5 to the level n=1.
To solve this, I used the equation 1/lamba=1.0974 * 10^7 m^-1*(1/n1^2-1/n2^2). I plugged in 1 for n1 and 5 for n2 and then solved for lamba. This gave me the answer .949x10^-9 nm. However, even if I change the number of sig figs, it is still wrong. Every time I work this problem out, I get the same answer. Can someone point out what I'm doing wrong?

Megan Singer 3D
Posts: 101
Joined: Wed Sep 30, 2020 9:33 pm
Been upvoted: 1 time

### Re: Sapling Week 2,3,4 #12

I've seen 1.0974 * 10^7 m^-1 given as a rydberg constant online before, but the number Dr. Lavelle gives us is R = 3.28984 × 10^15 Hz. I recommend using that and plugging it into ν = R [1/n1^2 - 1/n2^2]. Then convert frequency into wavelength using (frequency)(lambda) = c. I did that and I got 7.29 x10^-8 m, see if that works.

nayha a 1E
Posts: 63
Joined: Wed Sep 30, 2020 9:54 pm

### Re: Sapling Week 2,3,4 #12

I used the 1.0974x10^7 because that's what the feedback feature on Sapling told me to use. I figured out that I was just doing the nm conversion wrong. Thank you so much though!

Sedge Greenlee
Posts: 55
Joined: Wed Sep 30, 2020 9:35 pm

### Re: Sapling Week 2,3,4 #12

Hey, sorry as a general follow up question when converting from Hz to wavelength using the speed of light equation c=v(wavelength), is the result given in meters or nanometers?

Olivia Yang 3J
Posts: 65
Joined: Wed Sep 30, 2020 10:00 pm
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### Re: Sapling Week 2,3,4 #12

It should be given in meters! For ex like 2.10*10^-7 m but you can write it as 210 nm

Catie Donohue 2K
Posts: 69
Joined: Wed Sep 30, 2020 9:55 pm

### Re: Sapling Week 2,3,4 #12

Hi! Do you know when we should be using each equation as well as their different constant values to solve for the change in electron energy states? I've seen a lot of posts about it but I didn't see Professor Lavelle cover them in the lectures, so I was wondering if there were guidelines or recommendations for using each equation to solve for the change in energy states (I saw that he emphasized using the deltaE = -hR/n^2 - (-hR/n^2) in the lectures).

Thanks!

Arnav Saud 2C
Posts: 84
Joined: Wed Sep 30, 2020 9:51 pm

### Re: Sapling Week 2,3,4 #12

Sedge Greenlee wrote:Hey, sorry as a general follow up question when converting from Hz to wavelength using the speed of light equation c=v(wavelength), is the result given in meters or nanometers?

Depending on what the question is asking for, it can be either nm or m. For this question, it wanted to answer in nm (normally, it will ask for the answer in nm, but be prepared for a question asking it in m).

Ellison Gonzales 1H
Posts: 64
Joined: Wed Sep 30, 2020 10:00 pm

### Re: Sapling Week 2,3,4 #12

When Sapling would suggest using R=1.0974*10^7m^-1, it confused me a ton. But just to understand their reasoning, they only used this value for R when solving for wavelength to match the units for wavelength? But they did this just to fit all the work into one equation? Thank you!