# Bohr Model

could i get help or a formula for this question please

Use the Energy Levels for Hydrogen to calculate the wavelength corresponding to the following electron transition
Transition Energy in ev's Emitted wavelengths in m
2->1______ ________x10______

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quasar987
Homework Helper
Gold Member
Here's a formula you can use after you've discovered how many energy is contained in the photon emited during the transition of the electron

$$E=hf$$

where f is the frequency of the photon. How are frequency and wavelenght related?

taht is the question im as stumped as you are tahts all the info i have i had taht equation though it doesnt haev wavelength also how do i find the energy?

I dont think quasar is stumped, i think he was asking you a question which has an answer. The energy should be a given, or predicted by the bohr model. Think back to waves what other equation relates wavelength and frequency.

well speed of sound divided by wavelength =frequency

is taht what you were asking for?

A photon travels at the speed of _____

hf is the energy of the radiated photons

thats all i got

Ok, a photon travels at the speed of light. If its energy is given by hF, then the relationship

c = (Frequency)(Wavelength) should give you its wavelength. All you ahve to do is find the energy drop from 2->1 and solve this equation and plug it into the E = hF one.

quasar987
Homework Helper
Gold Member
well speed of sound divided by wavelength =frequency
This is also true for light. Light is a wave too, and a "photon" is only a fancy name we give to "little chuncks" (quanta!) of light.

So speed of light divided by wavelength =frequency.

k so correct me if im wrong 2-1 =-13.6 evs and w =-13.6evs/6.63e-34

?

quasar987
Homework Helper
Gold Member
k so correct me if im wrong 2-1 =-13.6 evs and w =-13.6evs/6.63e-34

?
-13.6 eV is the energy the electron has when it is in state n=1.

You're looking for the energy it has lost in going from state n=2 to state n=1, hence you want the difference between the energy of n=1 and the energy of n=2:

$$\Delta E = E_f - E_i$$

12.2? is that it? nope it was 10.2

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quasar987
Homework Helper
Gold Member
yeah.

-----------

hmm i got 1.15e53
10.2/1.6e-19/6.63e-34
its not right thought i think i missed soemthing
wait is this is my freqwuancy correcT?

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quasar987
Homework Helper
Gold Member
1 kg = 1000 grams, so 2.3 kg = 2.3*1000 = 2300 grams.

Same thing here: 1 eV = 1.6*10^19 J, so 12.2 eV = 12.2*1.6*10^-19 J.

ahhh i devided instead of multiplying

jtbell
Mentor
In problems like this it's easier to use Planck's constant in eV instead of joules:

$$\frac {10.2 eV} {4.14 \times 10^{-15} eV \cdot seconds}$$

jtbell said:
In problems like this it's easier to use Planck's constant in eV instead of joules:

$$\frac {10.2 eV} {4.14 \times 10^{-15} eV \cdot seconds}$$
=f=594574507617985878855444072835.38 correct?\
then speed of light/f=w
299 792 458/594574507617985878855444072835.38=5.04e-22

taht still doesnt give me the correct answer the correct answer is 1.22e-7

dextercioby
Homework Helper
Nope.It should be ~2.5 10^{15}Hz...And the wavelength ~1.22 10^{-7}m.

Daniel.

ahh yes by useing Planck's constant in its original form thanks for the help again guys

one mroe question on this the energy lvl of 3 in a hydrogen atom is -1.5 and lvl 1 is -13.6
though my graph shows the infinity sign and a 0.0 for where lvl 6 should be could i get the energy lvl of lvl 6 from someone? or how to get it

dextercioby
Homework Helper
U could have used the # given by J.T.I used,made that division correctly and wound up with the correct frequency...

Daniel.

i did do taht after i posted and tried useing the constant in ev form

Gokul43201
Staff Emeritus
How is $E_n$ related to $E_1 = -13.6~eV$ ?