Low amplitude (A) high frequency (f)

According to `common’ sense, which wave capsizes Mickey and the gang ? High amplitude (A) Low frequency (f) Low amplitude (A) high frequency (f) Let Mickey and friends be electrons in a metal

What actually happens in the photoelectric effect experiment High amplitude (A) Low frequency (f) Low amplitude (A) high frequency (f) Let Mickey and friends be electrons in metal

…so what is light if not a wave ?????? Einstein’s image…. LIGHT IS A “PHOTON” =A MASSLESS BULLET OF ENERGY OLD wave See also Figure 2.5 page 63 NEW Stream of photons

Planck’s equation: hf=Ephoton hf hf hf hf Stream of photons Doc’s analogy: 1 Photon is like a unit of coiled spring Highfrequency(high f)…high energy tight low frequency (low f)…low energy loose

What the `photon’ idea gives us… E(J)=hf(Hz) Planck’s Law Combined with… c=f*(m) => f= c Substitute into… wave equation  E= hc  Energy of light is now connected to the color (wavelength) of light Joules=J h=6.63*10-34 Joule *s

Which is the high energy end of the visible spectrum ? long wavelengths short wavelengths low f low E High f High E  Units in 10-9 m

In-class practice with using two versions of Planck’s Equation: Frequency f Energy E E(J/photon)=hf(Hz) =6.63*10-34*f(Hz) Wavelength  Energy E f= c/=> E(J/photon)= hc (m) =1.989*10-25(m) h=6.63*10-34 Joule *s c= 3.0*108 m/s

How does this help address the problems with the Rutherford atom? 1)Why don’t the p+and e- attract and come together ??? (or…why isn’t Earth the size of a golf ball?) help ??? 2)Why doesn’t the sun show all colors (e.g. show white light) when telescopes record spectrum? ???

Ask him ! (see also pp. 68-72) Niels “the Kid” Bohr at 27 soon after he makes his big theoretical breakthrough.

1913: The attack of the fifty foot Theoretical Physicist:Niels “the Kid” Bohr The `kid’s thinking… If light has wavelength but acts like a massless bullet, mass (specifically, an electron in an H atom) can have wavelengths too. (see also: on de Broglie’s hypothesis…. page 64 of text) Bohr at age 27 (when he makes his big breakthrough)

Using JUST MATH and Planck’s equation (no data) Bohr figures out a way to connect the orbital radius of an electron to a “wave” property of the electron. Text Figure 2.11 pg. 73

…the connection of integers to `waves’ leads him to the Bohr equation for the energy of electrons in Hydrogen (what’s burning in the Sun) and a radical new picture of electron orbits. n=3 n=2 EH(J)=-2.178*10-18 n2 n=1 Eq. 2.1 of text n=1,2,3…are integers defining circular orbits around positive nucleus

Bohr Model Predictions vs. Experiment ninf obs 434 486 656 Calc theory 434 486 656 5 2 4 2 3 2 n=5 1 4 2 3 0% error between observed and calculated !!! Observed H line (sun) spectrum (Balmer series) 3 2 52 42 Bohr’s `explanation of H spectrum’: quantum transitions between levels  =434486 656 nm

Bohr Model Predictions vs. Experiment (continued) Theoretical Computedradius of first H orbit: 5.20 nm Experimentally measured ground state radius of H: 0% error between observed and calculated (again) !!! 5.20 nm

Bohr’s Quantum jump pix Mr. electron sez FU…hell no I won’t go Light with different energy than E12 (even ifa tiny, tiny bit smaller) n=2 n=1 Light with exactly energy E12 Magic happens E12

How Bohr’s new way of thinking about matter bails out Rutherford 1)Why don’t the p+and e- attract and come together ??? (or…why isn’t Earth the size of a golf ball?) help ??? Electrons exist exclusively in defined circular paths at fixed distances from the nucleus

2)Why doesn’t the sun show all colors (e.g. show white light) when telescopes record spectrum? ??? help ???

Evolution of the atomic model so far…. • Thomson Model • 1897 Bohr Model 1913 • Philosophical • Magazine Series 6, • 21, 669-688 (1911) Philosophical Magazine Series 6 26. 1-25 (1913) Philosophical Magazine44, 295 (1897)

the quantum cat dilemma-one consequence of Bohr’s quantum concept Kitty state = = f1 1 + f22 (According to quantum physics) f1 ~ 1, but not quite f2 ~ 0 but not quite

Another animated, Abused quantum cat-in-a-box story….

What happened to chemistry ????? Walter White talking chemistry in “Breaking Bad”

The Bohr Model dies…1930 1930 Bohr theory The experimental chemists and spectroscopistssay “fugetabout” it. “typical” experimental spectroscopist/chemist Experimentalist’s attitude towards theoreticians: “If I want your opinion, I’ll give it to you…”

Bohr’s little Problem… 1930 Bohr theory Observed Na-`D’ line Is yellow Even worse.. Spectroscopists observe…. • 1)Bohr can’t predict anything right except H…the other elements have too many lines, e.g. Na BOHR 1 line predicted Bohr’s prediction: 1 green line 11lines !! 111 EXPERIMENT 11 LINES OBSERVED

Bohr model’s failures (continued) 2)…even Bohr’s predictions for H have problems • Can’t predict magnetic `fine’ structure of H, e.g • …magnetize H and even n=1splits into 2 lines 1 2 Turn on magnet near H  Not even the smartest theoretical physicists of the day (Sommerfeld, Planck, Dirac) can make 1=2 or 1=11…. with Bohr’s model

Link to atomic line spectra of elements…none of which Bohr can explain except H http://chemistry.bd.psu.edu/jircitano/periodic4.html

Evolution of the atomic model so far…. Bohr Model 1913 Thomson Model 1897 Philosophical Magazine Series 6 26. 1-25 (1913) Philosophical Magazine Series 6, 21, 669-688 (1911) Philosophical Magazine44, 295 (1897)

“Model 4: The spectroscopist’s atom My way or the highway… …or why we sing the spdf song The spectroscopists description of what they deduce from observingt lines is the `atom’

Low amplitude (A) high frequency (f)