Ch27.1 – Quantum Theory Diffraction - bending of waves around barriers.

Ch27.1 – Quantum Theory • Diffraction - bending of waves around barriers. • One proof light is a wave. • Double Slit Interference • Light of wavelength λ

Photoelectric effect - (Einstein’s Nobel Prize) • Classic theory: • Light is an E/M wave. • So even low energy light, with high intensity should liberate electrons • from “special” surface. • Red light didn’t liberate any electrons. • ‘special metal surface’

Photoelectric effect - (Einstein’s Nobel Prize) • Classic theory: • Light is an E/M wave. • So even low energy light, with high intensity should liberate electrons • from “special” surface. • Red light didn’t liberate any electrons. • Low intensity blue, however, could. • e-1

Photoelectric effect - (Einstein’s Nobel Prize) • Classic theory: • Light is an E/M wave. • So even low energy light, with high intensity should liberate electrons • from “special” surface. • Red light didn’t liberate any electrons. • Low intensity blue, however, could. • Violet also liberated electrons and gave a little KE to them. • e-1 • e-1

Photoelectric effect - (Einstein’s Nobel Prize) • Classic theory: • Light is an E/M wave. • So even low energy light, with high intensity should liberate electrons • from “special” surface. • Red light didn’t liberate any electrons. • Low intensity blue, however, could. • Violet also liberated electrons and gave a little KE to them. • Einstein explained: “Energy is quantized.” Comes in the form of photons • - little bundles of energy. • Red photons  low energy photons. • Blue photons  higher energy photons. • (Higher frequency = Higher energy) e-1 • E = h.f • e-1

Energy Equations: E = h.f Planck’s Constant: h = 6.626x10-34J.s The energy required to remove an electron is called the work function. E = h.fo 1 electron-Volt (eV) = 1.6x10-19 Joules (J) When the electron is hit by a high energy photon, the electron will eject from the atom and leave with the extra energy: extra energy energy of photon work function of atom

Ex1) A photon of red light has a frequency of 400 x 1012Hz. • What is its energy in joules? • Ex2) What is the energy of a 500nm green photon?

Ex1) A photon of red light has a frequency of 400 x 1012Hz. • What is its energy in joules? • E = h.f = (6.626x10-34J.s)(400x1012Hz) = 2.65x10-19J • Ex2) What is the energy of a 500nm green photon?

Ex3) Sodium has a threshold wavelength of 536nm. • a. What is the frequency? • b. What is the work function? • c. If 348nm UV light interacts with the electron, • how much energy does the electron leave with? • Ionization Energy (Work function) • e-1 • nucleus • Ch27 HW#1 1 – 5

Ch27 HW#1 1 – 5 • 1. How much energy for blue light that has a frequency of • 6.3 x 1014Hz. • 2. What is the energy of a 1m long radio wave? • 3. What is the energy of an Xray with wavelength = 1x10-10m?

Ch27 HW#1 1 – 5 • 1. How much energy for blue light that has a frequency of • 6.3 x 1014Hz. • E = h.f = (6.626x10-34J.s)(6.3x1014Hz) = 4.2x10-19J • 2. What is the energy of a 1m long radio wave? • 3. What is the energy of an Xray with wavelength = 1x10-10m?

4. Zinc has a threshold wavelength of 310nm. • a. What is the frequency? • b. What is the work function? • c. If 240nm UV light interacts with the electron, • how much energy does the electron leave with? • a. • b. • c.

4. Zinc has a threshold wavelength of 310nm. • a. What is the frequency? • b. What is the work function? • c. If 240nm UV light interacts with the electron, • how much energy does the electron leave with? • a. • b. E = h.f = (6.626x10-34J.s)(9.7x1014Hz) = 6.4x10-19J • c.

5. Cesium has a work function of 1.96eV. • a. What is the threshold wavelength? • c. If 425nm violet light interacts with the electron, • how much energy does the electron leave with? • a. • b.

Ch27.2 – Wave Nature of Particles • - by 1920’s proven that light acts as particle and a wave. • E/M radiation’s “wave/particle duality” • De Broglie thought this might be characteristic of all things • If the photons of E/M radiation travel as transverse waves • and exhibit particle behaviors, • then matter in motion must exhibit wave behavior • DeBroglie • Wavelength: • momentum • Ex1) Calculate the wavelength of a baseball (m = 0.25kg) hit at 21 m/s. • Ex2) Calculate the wavelength of an electron traveling at • half the speed of light. • (r = 0.053nm)

Heisenberg’s Uncertainty Principle • Electrons are so small, you can’t know both their location and • momentum. If you know its location, you don’t know where its going. • If you know where it’s going, you won’t know where it is along its path. • Ch27 HW#2 6 – 9

Ch27 HW#2 6 – 9 • 6) I have a mass of 75kg walking at 1 m/s. Find De Broglie λ. • 7) An electron (m=9.11x10-31kg) with speed of 4.3x106 m/s. Find λ.

8) A 7.0kg bowling ball rolls with a velocity of 8.5 m/s. • a) Find λ. • b) Why don’t we see it wiggle? • 9) X-ray has a wavelength of 5.0x10-12m. • a) calc its mass • b) why does it exhibit little particle behavior?

Ch28.1 – The Atom • History: • 1800’s – Millikan’s Oil Drop Experiment found the charge • of an electron. • - Cathode Ray Tube – found electron mass • 1900’s – JJ Thompson’s Plum Pudding Model of the atom • - Rutherford’s Gold Foil Experiment (1905) • Atoms are mostly empty space • with a dense core, called it nucleus. • - Bohr’s Planetary Model of the atom • Electrons have discrete energy levels • and cannot be found in between. • They can only absorb 1 photon, jump • to excited state, return and release photons. • - Current model: have a wiggle and energy levels • are complicated paths.

Ex1) An electron in an excited state of the hydrogen atom drops from • the second energy level to the first, as shown. • Calc the energy, frequency, and wavelength of the photon released. • e-1 E2 = 13.6eV • E1 = 3.4eV • a) • b) • c)

Ex1) An electron in an excited state of the hydrogen atom drops from • the second energy level to the first, as shown. • Calc the energy, frequency, and wavelength of the photon released. • e-1 E2 = 13.6eV • E1 = 3.4eV • a) 13.6 – 3.4 = 10.2eV • b) • c)

HW #2) An electron in an excited state of Mercury drops from 8.82eV • to 6.67eV. • Calc the energy, frequency, and wavelength of the photon released. • e-1 E2 = 8.82eV • E1 = 6.67eV • Ch28 HW#1 1 – 5

HW #2) An electron in an excited state of Mercury drops from 8.82eV • to 6.67eV. • Calc the energy, frequency, and wavelength of the photon released. • e-1 E2 = 8.82eV • E1 = 6.67eV • a) E = 8.82 – 6.67 = 2.15eV • b) • Ch28 HW#1 1 – 5

Lab 28.1 – Atomic Spectra • - due tomorrow • - Ch18 HW#1 due at beginning of period

Ch28 HW#1 1 – 5 • 1. The diameter of the hydrogen nucleus is 2.5x10-15m and the distance • to the first energy level is ~ 5x10-9m. If a baseball has a diam of 7.5cm • and it represents the nucleus, how far away would the first energy level be?

3. An electron in H drops from 11.6eV to 5.1eV. • Calc the energy, frequency, and wavelength of the photon released. • e-1 E2 = 11.6eV • E1 = 5.1eV • a) 11.6 – 5.1 = 6.5eV • b) (E=hf) • c) (c=λf)

4. Emitted photon is orange at 600nm. Calc frequency and energy. • a) (c=λf) • b) (E=hf)

5. Emitted photon is blue-green at 490nm. Calc frequency and energy. • a) (c=λf) • b) (E=hf)

Ch30.1 – The Nucleus • Atomic particles: Location Charge Mass • Proton Inside nucleus (+1) 1 a.m.u. • Neutron Inside nucleus (0) 1 a.m.u. • ElectronOutside nucleus (+1) 0.0005 a.m.u. • Atoms  radius ~ 10–10m, • nucleus is 10,000 times smaller • yet 99.9% of mass is there • - density of nucleus = 2.3x1017 kg/m3 • - nuclides act like a swarm of bees • What holds it together? v v

Ch30.1 – The Nucleus • Atomic particles: Location Charge Mass • Proton Inside nucleus (+1) 1 a.m.u. • Neutron Inside nucleus (0) 1 a.m.u. • ElectronOutside nucleus (+1) 0.0005 a.m.u. • Atoms  radius ~ 10–10m, • nucleus is 10,000 times smaller • yet 99.9% of mass is there • - density of nucleus = 2.3x1017 kg/m3 • - nuclides act like a swarm of bees • What holds it together? • Strong Nuclear Force! • - takes ~ 8,000,000 eV to remove a nucleon • (compare to removing an electron from H = 13.6 eV) • Isotopes - same element (same # protons) differ in # of neutrons. • Ex1) How many nuetrons in iron isotope: 5626Fe? • Ex2) Write the symbol for chlorine-36. v v

Radioactive Decay • Alpha Decay – alpha particle emitted from nucleus (42He or 42α) • 23892U  42α + ____ 42α are low energy • Beta Decay – beta particle emitted (0-1β or 0-1e) • 10n  11p + ____ 0-1β are mid energy • Gamma Decay – high energy photon released (γ) • Ex3) Write the eqn for the radioactive decay of Radium-226 that emits an alpha particle and becomes radon. v v

Ex4) Write the eqn for the radioactive decay of lead-209 • into bismuth-209. • Half Life – time it takes for half of a radioactive sample to decay: • Exs:Hydrogen-3: 12.3 yrs • Carbon-14: 5730 yrs • Uranium-235: 710,000,000 yrs • Ex5) Half life of fluorine-17 is 66sec. If you have a 32g sample, how much will be left after 4min 24sec?

The Energy of Matter E = mc2 • Ex6) How much energy is released if an electron of mass 9.11x10-31kg • is completely turned into energy? • Nuclear fission – 1 atom breaks into smaller pieces • Nuclear fusion – nuclei combine together • Ch30 HW#1 • Ch30 HW#2 • Ch27-30 Rev • (No Rev day, test tomorrow)

Ch27.1 – Quantum Theory Diffraction - bending of waves around barriers.