# Quick little Gen Chem Question about Wavelength and Freq

#### Mrhyde

##### Becoming Dr. Jekyll
I have gotten all these type of questions correct but find confusion on this particular question:

Which of the following transitions in a hydrogen atom represent absorption of the smallest frequency photon?
A) n=1 to n=2
b) n= 5 to n =6
C) n= 4 to n=1

Thought Process :
Obviously we can eliminate C immediately because Absorption's go "upwards".

So now my dilemma is choosing between A and B ? usually on all these questions the answers have not been so close as they are here, so that's why I am confused since an obvious difference between A and B does not "jump" out at me.

So I know the smallest frequency would be equal to which has the smallest amount of energy which is also equal to which has the smallest gap between the answer choices ( since the bigger the gap the more energy )

--> But A and B are both at a difference of one, so they are both the same small gap apart ?

----> The answer is B n= 5 to n =6 .... but why ? are smaller numbers that are closer to the number 1, considered Higher Energy or something ?

OP

#### Mrhyde

##### Becoming Dr. Jekyll

You're correct that the associated energy with the n = 1 -> 2 transition is the highest; however, the question asks for the lowest frequency of the absorbed photon. Since E = hv (Planck's equation) where v = frequency, energy is proportional to frequency. As such, you want to find the absorption transition with the lowest energy, thus B! Hope that helps
Before I even get a chance to read your answer which I will read it right now , HOW ON EARTH DID YOU ANSWER SO QUICKLY AND ANSWER WITH THE TIME TO MAKE A DRAWING lol I literally just clicked submit and its been up for 20 seconds hahaha thats amazing. I'll read your answer now, thank you

OP

#### Mrhyde

##### Becoming Dr. Jekyll

You're correct that the associated energy with the n = 1 -> 2 transition is the highest; however, the question asks for the lowest frequency of the absorbed photon. Since E = hv (Planck's equation) where v = frequency, energy is proportional to frequency. As such, you want to find the absorption transition with the lowest energy, thus B! Hope that helps
AWESOME answer man I appreciate this alot thank you. ! So Its true then, that anything close to the #1 will be considered higher energy ?

OP

#### Mrhyde

##### Becoming Dr. Jekyll
You got it. Essentially, transitions from low energy states to high energy states have greater associated energies when the transition sets have lower n values. n = 1 -> 2 transition always has the highest associated energy (absorption and emission).
Awesome I understand it perfectly now thank you

maga1994
OP

#### Mrhyde

##### Becoming Dr. Jekyll
You got it. Essentially, transitions from low energy states to high energy states have greater associated energies when the transition sets have lower n values. n = 1 -> 2 transition always has the highest associated energy (absorption and emission).
By the way just out of curiosity, do you know what topic in gen chem this would be considered ?

#### P0W3RL1FT3R

5+ Year Member
Excuse my ignorance, but is a small frequency the same as saying a long wavelength?