## Rydberg constant

ALee_1J
Posts: 86
Joined: Wed Sep 30, 2020 9:32 pm

### Rydberg constant

On the Constants and Equations sheet, the Rydberg constant = 3.289 x1015 but Sapling says that it's 1.097 x 107? I'm confused as to why that is and which is correct?

Meghan Krushena 2E
Posts: 65
Joined: Wed Sep 30, 2020 10:10 pm

### Re: Rydberg constant

I am not sure why it is not consistent, but the reason for the two different numbers is the units it is in. When R=3.28984 x 10^15 it is in Hertz (given on the equation/constant sheet) but the number that appears on sapling (1.097 x 10^7) is in meters. Hope this helps!

Frankie Mele 3J
Posts: 73
Joined: Wed Sep 30, 2020 10:09 pm

### Re: Rydberg constant

ALee_3G wrote:On the Constants and Equations sheet, the Rydberg constant = 3.289 x1015 but Sapling says that it's 1.097 x 107? I'm confused as to why that is and which is correct?

Sapling uses 1.097x10^7 when setting the equation equal to 1/lambda, whereas the constant 3.289x10^15 is used when the equation is set equal to frequency(v). This is because frequency can be rearranged to v=c/lambda and the Rydberg constant 3.289x10^15 divided by c (the speed of light) results in the constant 1.097x10^7 (R/c). Hope this helps!

Mirren Solomon Discussion 2G
Posts: 51
Joined: Wed Sep 30, 2020 9:39 pm

### Re: Rydberg constant

3.289 x1015 is the constant that is mainly used in the v=R[1/nI^2-1/n2^2] equation. Sapling may use different units if there are different starting values.

Sophia Spungin 2E
Posts: 67
Joined: Wed Sep 30, 2020 9:41 pm

### Re: Rydberg constant

Im pretty sure thats just R/c, which allowed you to set the equation equal to 1/wavelength

Colin Squire 3B
Posts: 65
Joined: Wed Sep 30, 2020 9:35 pm

### Re: Rydberg constant

When using the equation, c="lambda"*v, and solving for frequency (c/lambda), the speed of light is value is divided to the Rydberg constant when it is 3.289e15. This gives the value 1.097e7. Essentially the equation is rewritten to equal 1/lambda.

AustinMcBrideDis3L
Posts: 66
Joined: Wed Sep 30, 2020 9:39 pm

### Re: Rydberg constant

I believe the Sapling explanation is using different units. To be safe for midterms and the final just use the number and units given on the equation sheet we are allowed to use.

Emma Chang 1G
Posts: 52
Joined: Wed Sep 30, 2020 10:02 pm

### Re: Rydberg constant

I believe R = 3.28984 x 10^15 is used for the equation v = R[(1/n1^2)-(1/n2^2)]. I think they get 1.0966 x 10^7 when they set the equation equal to 1/λ instead of v. Since v = c/λ, you could write the equation as c/λ= R[(1/n1^2)-(1/n2^2)], and then you would divide c over to get 1/λ= (R/c)[(1/n1^2)-(1/n2^2)]. I think R/c would then be 1.0966 x 10^7/m.

I think Dr. Lavelle said in one of the lectures that he prefers to use the equation with the Rydberg constant that's on the formula sheet, so that's what I would go with! Hope this helps!