## Atomic Spectra Post-Module Question

H-Atom ($E_{n}=-\frac{hR}{n^{2}}$)

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Fiona Latifi 1A
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Joined: Sat Sep 14, 2019 12:16 am

### Atomic Spectra Post-Module Question

#38 on the Atomic Spectra Post-Module Assessment asks us to calculate the frequency of a photon emitted by a hydrogen atom when an electron makes a transition from the fourth to the second principal quantum level.

A. -6.17 x 10^14 Hz

B. 1.62 x 10^-15 Hz

C. 6.17 x 10^14 Hz

D. 2.71 x 10^-52 Hz

I keep getting option A (-6.17 x 10^-14, which is incorrect. Can anyone explain the correct answer? Thank you!

Chem_Mod
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### Re: Atomic Spectra Post-Module Question

Please show us your work/thought process so that we can better assist you with this problem :)

Mashkinadze_1D
Posts: 87
Joined: Sat Aug 24, 2019 12:15 am

### Re: Atomic Spectra Post-Module Question

Although I may be incorrect, I believe what is wrong with your answer is the -6.17 x 10^14 as a frequency cannot be negative. If I am incorrect, I hope someone else can show the correct answer so I can have a better understanding too, but if I am, hope this helps!

Jessica Li 4F
Posts: 115
Joined: Fri Aug 09, 2019 12:16 am

### Re: Atomic Spectra Post-Module Question

I agree with the above answers. Although you get a negative value for frequency when you calculate using the equation, it is because frequency is emitted and therefore "lost." When anything is "lost," it will be expressed as a negative value in an equation. However, the actual frequency has to have a positive value, as frequency cannot plausibly be negative. Therefore, the correct answer is actually C. (which is just the positive value of answer choice A).

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