chapter 27- atomic/quantum physics. the sun why do we see the sun as yellow instead of green or...
TRANSCRIPT
![Page 1: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/1.jpg)
Chapter 27- Chapter 27- Atomic/Quantum PhysicsAtomic/Quantum Physics
![Page 2: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/2.jpg)
The SunThe Sunhttp://soho.nascom.nasa.gov/
Why do we see the sun as yellow instead of green or blue or pink?
![Page 3: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/3.jpg)
Blackbody SpectrumBlackbody Spectrum
![Page 4: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/4.jpg)
Photon Theory of LightPhoton Theory of LightLight is transmitted as tiny
particles called photons
The amount of energy in a photon depends on its frequency
pchc
hfE
h= Planck’s Constant= 6.626 x 10-34 Jsf= frequency of lightc= speed of lightλ= wavelengthp= momentum
![Page 5: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/5.jpg)
The Photoelectric EffectThe Photoelectric EffectWhen light shines on a metal
surface, electrons are emitted from the surface
![Page 6: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/6.jpg)
Photocells (p.829)Photocells (p.829)When the
photocell is in the dark, the ammeter reads 0 (no current)
When light with a high enough frequency shines on the current flows in the circuit
![Page 7: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/7.jpg)
PhotocellsPhotocellsKEmax of the emitted electrons
can be found by reversing the voltage and making the C electrode negative
The electrons are repelled by C, but the fastest electrons will still make it across
There is a minimum voltage, Vo, called the stopping voltage. No current will flow if the voltage is less than the stopping voltage
Kemax = e Vo
![Page 8: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/8.jpg)
Photoelectric EffectPhotoelectric EffectEinstein’s Theory Predicts:
◦ Increasing the intensity of the light does not make the electrons go faster. This is because although more photons are striking
the surface, they have same energy
◦ Increasing the frequency of the light beam increases the energy of the photons which changes the maximum KE of the ejected electrons
oo WhfhfhfKE max
![Page 9: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/9.jpg)
Photoelectric EffectPhotoelectric EffectThe work function, Wo, is the
minimum amount of energy necessary to get an electron off the surface of the metal
fo is the “cutoff” frequency. If the light beam’s frequency is below that, then no electrons will be emitted
oo hfWE
![Page 10: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/10.jpg)
Compton EffectCompton EffectA.H. Compton scattered
xrays from various materials◦ Found out that the
scattered light had a lower frequency than incident light
◦ Since frequency decreases, wavelength increases
Used conservation of momentum to determine that the photon transfers some of its energy to the electron
![Page 11: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/11.jpg)
de Broglie Wavelengthde Broglie WavelengthLight sometimes behaves like a
wave and sometimes like a particle
Louis de Broglie came up with the idea that particles might also have wave properties
mv
h
p
h
De Broglie wavelength of a particle
![Page 12: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/12.jpg)
de Broglie Wavelengthde Broglie WavelengthThe wavelength of large objects
is very small
For a 0.20 kg ball travelling at 15 m/s
mxsmkg
Jsx 3434
102.2/1520.0
106.6
![Page 13: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/13.jpg)
de Broglie Wavelengthde Broglie WavelengthDetermine the wavelength of an
electron that has been accelerated through a potential difference of 100 V
2
2
1mvqV
s
mx
m
qVv 6109.5
2
mx
sm
xkgx
Jsx
mv
h 10
631
34
102.1)109.5)(101.9(
1026.6
![Page 14: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/14.jpg)
Davisson-Germer Davisson-Germer ExperimentExperimentThe spacing of atoms in a crystals
is on the order of 10-10 m, so one could be used as a diffraction grating
In 1927, Davisson and Germer scattered electrons from the surface of a metal crystal. The wavelength they got matched the predicted de Broglie wavelength
![Page 15: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/15.jpg)
Bohr Model of the AtomBohr Model of the AtomElectrons orbit the nucleus in
circular orbits called stationary states
When an electron jumps from one state to another, light is either absorbed or emitted
The energy required to go between states is a fixed amount
![Page 16: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/16.jpg)
Bohr Model of the atomBohr Model of the atomIf an electron jumps from a
higher state to a lower state, it emits a single photon of light
statelower ofEnergy -stateupper ofEnergy EnergyPhoton lu EEhf
![Page 17: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/17.jpg)
Energy Level Diagram (p. Energy Level Diagram (p. 847)847)
n= 1is ground state, n=2,3,4.. Are excited states
To completely free an electron in the ground state, you’d need to put in 13.6 eV of energy (ionization energy of Hydrogen)
![Page 18: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/18.jpg)
Energy Level DiagramEnergy Level DiagramHow much
energy to go from ground to n=2?
How much energy to go from n=2 to n=4?
eVeVeV 2.104.36.13
eVeVeV 55.285.04.3
![Page 19: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/19.jpg)
Energy Level DiagramsEnergy Level DiagramsWhat are the
possible transitions for an electron in excited state n=3?◦31◦32◦21
![Page 20: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/20.jpg)
Emission SpectraEmission SpectraA material’s emission spectrum
show the wavelengths of the photons emitted when electrons jump to lower energy states
![Page 21: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/21.jpg)
Absorption SpectraAbsorption SpectraThe absorption spectrum of a
material shows that gases can absorb light at the same frequencies at which they emit
![Page 22: Chapter 27- Atomic/Quantum Physics. The Sun Why do we see the sun as yellow instead of green or blue or pink?](https://reader035.vdocument.in/reader035/viewer/2022081603/56649f315503460f94c4cf72/html5/thumbnails/22.jpg)
Absorption/Emission Absorption/Emission SpectraSpectra