Introductory Bohrs Model Problem and I'm Lost

[zoiberg137]

Introductory Bohrs Model Problem...and I'm Lost!

Ok, so I "think" what I am trying to find here is the frequency of the energy between two states of energy. I admit that part of my problem probably lies in the fact that I'm not even sure what it is I'm trying to find. My class seems to be just speeding through this material. But this is my first science class since I dropped out of my first year of high school...so I'm probably a little behind! Anyway...

So I need to find the frequency between E5 and E3. I understand how to use the formula E5=13.6(1-1/25)=13.056eV.

And so the difference between E5 and E3 is .97.

Simple enough.

And then we have to convert that to joules so we multiply it by 1.6E-19 in order to get 1.552E-19 joules.

And then I THINK I am supposed to use the formule F=E/H in order to find the frequency. But when I divide 1.552E-19 joules by the constant 6.63E-34 joules, I get 2.34E-54.

The problem here is that I know my answer is supposed to be 1288.

What am I missing here??

 

[mynick]

I divide 1.552E-19 joules by the constant 6.63E-34 joules, I get 2.34E-54.

The problem here is that I know my answer is supposed to be 1288.

What am I missing here??

correct answer is:

(1.552E-19)/(6.63E-34)=2.34E+14 Hz

(a.k.a 2.34*10^5 THz, where T means Terra)

 

[zoiberg137]

ok so i get how it comes to 2.34E14, I wasn't using parenthesis. Silly mistake!

But I'm not sure what you are doing to get terra hz, or why, as I know my instructor never mentioned that term. Nor my book for that matter.

Also, how is 1288 an acceptable answer?

Thoughts??

 

[zoiberg137]

AHHH! I get it. sort of.

So from 2.34E14 hz I need to use this frequency to find the wavelength.

Using the formula lambda= C/F, with speed of light as my constant, I get 1282E-6. This is REALLY close to my target of 1288!

I just seem to be missing one last final step. I'm guessing I need to convert the hz into something else before dividing it by a unit of time.

Anyone know what I'm missing?

 

[mynick]

AHHH! I get it. sort of.

So from 2.34E14 hz I need to use this frequency to find the wavelength.

Using the formula lambda= C/F, with speed of light as my constant, I get 1282E-6. This is REALLY close to my target of 1288!

I just seem to be missing one last final step. I'm guessing I need to convert the hz into something else before dividing it by a unit of time.

Anyone know what I'm missing?

c= λ*f => λ=c/f => λ=(3*10Ε+8)/(2.34Ε+14) => λ=0.00000128205 meters ,which abbreviated can be written as:
λ= 1282 nm ( where 'n' means nano=10E-9)

it is not 1288 because you rounded the results in the previous calculations...

 

[zoiberg137]

AHH! Now I totally get it. Thank You!

That was fun. Both discouraging and yet encouraging at the same time...