1. White Light - Dispersion
The separation of white light into it’s different colors!!!!

2. Electromagnetic Spectrum

3. Continuous Spectrum

4. Gases and Spectra

5. Discrete Emission Spectrum

6. A quick review of the atom model
Democritus: “Atom” = indivisable particle
JJ Thomson: (~1827) Plumb pudding model
Rutherford: (~1909) + nucleus – gold foil experiment
Bohr : Spectral lines imply E levels of e- s

7. More Bohr ing material 0 n = ∞ .85 n = 4 1.5 n = 3 E ev 3.4 n = 2
E of level = / n2
( for hydrogen atoms)
When e- drop down E level they release difference of E ass. with those E levels
n2  n1 = 13.6 – 3.4 = 10.2 ev of E given off
E release is specific ammt. = quantized = packet of E = particle!

8. So then:
From n =4, how many possible discrete Energy transitions might an
involved with an electron ending up at n = 1??????

9. Did you say 6???? Then take a bow son!
*** I would know how to do this if I were you eh!

10. Hydrogen Spectra

11. How can we calculate the wavelength of the E released?
With this handy equation that takes into consideration the
Energy transitions. (for hydrogen atoms)
1 / λ = R ( 1 / nf / no2 )
R = Rydberg constant = x 10 7 m

12. Hey I have a great idea – why don’t you calculate the wavelength for a n = 3 to n = 2 transition (in a hydrogen atom).

13. Did you find
λ = 6.56 x 10-7 m
= 656 nm
= red

14. What energy (in ev) is associated with this transition?

15. Did you calculate
1.9 ev
Great!!!!

16. EMISSION SPECTRA

17. HYDROGEN EMISSION SPECTRA

18. CONTINUOUS EMISSION SPECTRUM
LINE EMISSION SPECTRUM
LINE ABSORPTION SPECTRUM

19. The last model we will discuss here is DeBroglie (~1924)
A particle needs to be moving to have a wavelength
mc2 = E/photon = hf = h (c / λ) because f = c / λ
h = Plank’s constant = x
From mc2 = h (c / λ ) we get mc = h / λ
Recall that mc = mv = p (momentum)
Finally we can derive λ = h / mv

20. Demonstrations
Phet.colorado.edu
Color Vision
Neon Lights
Radio Waves