MAPLE TA 25_3

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MAPLE TA 25_3

Post  phygirl. on Thu Apr 23, 2009 2:07 am

I think we should get another head start on the next quiz. Here are the questions. I'm going to start working them out, I'll report back with progress. Feel free to help!!


1. What is the total (total refers to kinetic + potential here) energy (in eV) of the electron in the Bohr model for a hydrogen like atom (all but one electrons removed) with Atomic Number (number of protons or electrons in the neutral atom) 3 in its lowest state, the "ground state" (sheet 35,36') ? Include the correct sign of the energy.


2. A hydrogen atom makes a transition from a state with quantum number 9 to a state with quantum number 5. Indicate with a negative (positive) sign whether the atom loses (gains) energy and calculate the energy in eV (sheet 36).


3. In an X-ray tube electrons traverse an accelerating voltage of 16.74 kilovolts. What is the minimum wavelength of the X-ray photons in nm (sheet 39) ? Indicate with a positive (negative) sign whether the photons belong to the continuous (discrete, quantized) part of the X-ray spectrum.

4. The atomic number of the anode (the positively charged plate emitting the X-rays) material is 69. What is the wavelength of the K-alpha photons emitted in nm when the atom makes a transition from the n=2 to the n=1 state (sheet 40') ? Indicate with a positive (negative) sign whether the photons belong to the continuous (discrete, quantized) part of the X-ray spectrum.

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1-3

Post  jsyz on Thu Apr 23, 2009 9:01 am

1.)-
En=-13.6eV*(Z^2/n^2)
Z=number given
n=1
so answer=-13.6*(number given)^2
2.)-
Delta E=13.6eV*((1/n1^2)-(1/n2^2))
just plug in the n1 & n2
3.)+
V=h*c/wavelength(min)*e----->wavelength(min)=h*c/V*e
V is given in kilovolts(remember to convert it to volts)
wavelength=(6.63E-34*3E8)/(V(given)*1.6E-19)
they want the answer in nm so divide the answer by 1E-9
still working on #4


Last edited by jsyz on Thu Apr 23, 2009 9:35 am; edited 3 times in total

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#4

Post  jsyz on Thu Apr 23, 2009 9:34 am

4.) -
f=(3/4)(13.6/h)(Z-1)^2
Z=# given
h=4.14E-15
c=wavelength*f =====>wavelength=c/f
they want answer in nm
so divide answer by 1E-9

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Question 3

Post  Guest786 on Thu Apr 23, 2009 3:53 pm

I am having trouble with this problem.

In an X-ray tube electrons traverse an accelerating voltage of 15.39 kilovolts. What is the minimum wavelength of the X-ray photons in nm (sheet 39) ? Indicate with a positive (negative) sign whether the photons belong to the continuous (discrete, quantized) part of the X-ray spectrum.

this is what i did:

15.39 kilovolts= 15390 volts

(6.34E-34*3E8)/(15390*1.6E-19) then i divided that answer with 1E-19 and it doesnt work. My final answer came to be .0772417154. What am i doing wrong?

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#4

Post  physhelp on Thu Apr 23, 2009 3:55 pm

I was able to get the answer but can someone explain why h is not plancks constant but (6.63*10^-34)/(1.9*10^-19)= 4.14*10^-15

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question 3

Post  guest786 on Thu Apr 23, 2009 4:00 pm

nevermind i found my problem

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#4

Post  k8 on Thu Apr 23, 2009 4:28 pm

I'm getting #4 wrongggg whyyy??? help

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Reasoning for h

Post  crackhea on Fri Apr 24, 2009 12:51 am

the h we're used to using is 6.626E-34 J s although the units for number 4 we're using eV, so the constant becomes 4.136E-15 eV s

for anyone getting number 4 wrong try using 4.1356E-15 as your h rather than 4.14E-15

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Re: MAPLE TA 25_3

Post  aaa on Fri Apr 24, 2009 4:06 pm

I am not getting #4

wat is the final answer came to be, to wat power?

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Re: MAPLE TA 25_3

Post  soso on Fri Apr 24, 2009 4:55 pm

i can't get 4 either

helppppp

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