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

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Presentation on theme: "Ch27.1 – Quantum Theory Diffraction - bending of waves around barriers. One proof light is a wave. Double Slit Interference Light of wavelength λ."— Presentation transcript:

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

2 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’

3 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

4 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

5 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

6 Energy Equations: E = h. f Planck’s Constant: h = 6.626x J. s The energy required to remove an electron is called the work function. E = h. f o 1 electron-Volt (eV) = 1.6x 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

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

8 Ex1) A photon of red light has a frequency of 400 x Hz. What is its energy in joules? E = h. f = (6.626x J. s)(400x10 12 Hz) = 2.65x J Ex2) What is the energy of a 500nm green photon?

9 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

10 1. How much energy for blue light that has a frequency of 6.3 x Hz. 2. What is the energy of a 1m long radio wave? 3. What is the energy of an Xray with wavelength = 1x m?

11 Ch27 HW#1 1 – 5 1. How much energy for blue light that has a frequency of 6.3 x Hz. E = h. f = (6.626x J. s)(6.3x10 14 Hz) = 4.2x J 2. What is the energy of a 1m long radio wave? 3. What is the energy of an Xray with wavelength = 1x m?

12 Ch27 HW#1 1 – 5 1. How much energy for blue light that has a frequency of 6.3 x Hz. E = h. f = (6.626x J. s)(6.3x10 14 Hz) = 4.2x J 2. What is the energy of a 1m long radio wave? 3. What is the energy of an Xray with wavelength = 1x m?

13 Ch27 HW#1 1 – 5 1. How much energy for blue light that has a frequency of 6.3 x Hz. E = h. f = (6.626x J. s)(6.3x10 14 Hz) = 4.2x J 2. What is the energy of a 1m long radio wave? 3. What is the energy of an Xray with wavelength = 1x m?

14 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.

15 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.

16 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 = (6.626x J. s)(9.7x10 14 Hz) = 6.4x J c.

17 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 = (6.626x J. s)(9.7x10 14 Hz) = 6.4x J c.

18 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.

19 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.

20 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.

21 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)

22 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)

23 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

24 6) I have a mass of 75kg walking at 1 m/s. Find De Broglie λ. 7) An electron (m=9.11x kg) with speed of 4.3x10 6 m/s. Find λ.

25 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=9.11x kg) with speed of 4.3x10 6 m/s. Find λ.

26 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=9.11x kg) with speed of 4.3x10 6 m/s. Find λ.

27 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 5.0x m. a) calc its mass b) why does it exhibit little particle behavior?

28 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 5.0x m. a) calc its mass b) why does it exhibit little particle behavior?

29 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 5.0x m. a) calc its mass b) why does it exhibit little particle behavior?

30 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.

31 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 E 2 = 13.6eV E 1 = 3.4eV a) b) c)

32 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 E 2 = 13.6eV E 1 = 3.4eV a) 13.6 – 3.4 = 10.2eV b) c)

33 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 E 2 = 8.82eV E 1 = 6.67eV Ch28 HW#1 1 – 5

34 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 E 2 = 8.82eV E 1 = 6.67eV a) E = 8.82 – 6.67 = 2.15eV b) Ch28 HW#1 1 – 5

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

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

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

38 3. An electron in H drops from 11.6eV to 5.1eV. Calc the energy, frequency, and wavelength of the photon released. e -1 E 2 = 11.6eV E 1 = 5.1eV a) 11.6 – 5.1 = 6.5eV b) (E=hf) c) (c=λf)

39 3. An electron in H drops from 11.6eV to 5.1eV. Calc the energy, frequency, and wavelength of the photon released. e -1 E 2 = 11.6eV E 1 = 5.1eV a) 11.6 – 5.1 = 6.5eV b) (E=hf) c) (c=λf)

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

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

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

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

44 Ch30.1 – The Nucleus Atomic particles:LocationChargeMass ProtonInside nucleus (+1)1 a.m.u. NeutronInside nucleus (0)1 a.m.u. ElectronOutside nucleus (+1) a.m.u. Atoms  radius ~ 10 –10 m, nucleus is 10,000 times smaller yet 99.9% of mass is there - density of nucleus = 2.3x10 17 kg/m 3 - nuclides act like a swarm of bees What holds it together? vv

45 Ch30.1 – The Nucleus Atomic particles:LocationChargeMass ProtonInside nucleus (+1)1 a.m.u. NeutronInside nucleus (0)1 a.m.u. ElectronOutside nucleus (+1) a.m.u. Atoms  radius ~ 10 –10 m, nucleus is 10,000 times smaller yet 99.9% of mass is there - density of nucleus = 2.3x10 17 kg/m 3 - 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: Fe? Ex2) Write the symbol for chlorine-36. vv

46 Radioactive Decay Alpha Decay – alpha particle emitted from nucleus ( 4 2 He or 4 2 α) U  4 2 α + ____ 4 2 α are low energy Beta Decay – beta particle emitted ( 0 -1 β or 0 -1 e) 1 0 n  1 1 p + ____ 0 -1 β 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. vv

47 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?

48 The Energy of Matter E = mc 2 Ex6) How much energy is released if an electron of mass 9.11x kg 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)


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