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Waves, Light, Quantum. Figure 4.1: Molar Volume (elements known in 1869) (a few more recently discovered elements added)

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Presentation on theme: "Waves, Light, Quantum. Figure 4.1: Molar Volume (elements known in 1869) (a few more recently discovered elements added)"— Presentation transcript:

1 Waves, Light, Quantum

2 Figure 4.1: Molar Volume (elements known in 1869) (a few more recently discovered elements added)

3 Other Periodic Trends

4 View of White Light Through Spectroscope (Investigate This 4.5) white light viewed through slit light separated into different wavelengths by diffraction grating

5 white light source covered with permanganate solution KMnO 4 View of White Light Source Through KMnO 4 Solution (Investigate This 4.5)

6 Color of Wavelengths Absorbed is Complementary To Color Observed Purple Appearing Light

7 Emission vs. Absorption (Consider This 4.7) light source white light source some matter (light absorber) prism (wavelength separator)

8 Light = Electromagnetic Waves Electromagnetic radiation the emission and transmission of energy in the form of electromagnetic waves

9 one cycle wavelength amplitude Properties of Waves = wavelength = length of one cycle  frequency = number of cycles/time

10 Properties of Waves c = velocity of light wave in vacuum = 3.00 x 10 8 m/s x  c

11  = c/ = ( 3.00 x 10 8 m/s) / 4.69 x Hz = 6.40 x m Problem 4: A laser used to weld detached retinas produces light with frequency of 4.69 x Hz. What is this wavelength in nm? To what part of the electromagnetic spectrum does this light belong? (1Hertz = 1 s -1.)  = 640 nm (red region of visible spectrum)

12

13 Waves In a Ripple Tank (Investigate This 4.12, 4.16) Click on ripple tank wave simulation ripple tank wave simulation For 4.12 Set to Setup: Single Source; 1 Src, 1 Freq; Color Scheme 3 For 4.16 Change Setup to Double Slit (source automatically switches to 1 Plane Src, 1 Freq)

14 Planck’s Quantum Theory

15 Planck’s Basic Ideas E states of a system (e.g., atom) are quantized, not continuous E Classical Physics View continuous E states state 3 state 2 state 1 Planck’s Quantum View quantized E states

16 Planck’s Basic Ideas Only certain E increments may be absorbed or emitted by system E Classical Physics View continuous E states infinite #of  E possible state 3 state 2 state 1 Planck’s Quantum View only transitions allowed are between quantized E states emissions

17 Planck’s Basic Ideas Energy is emitted or absorbed in discrete units (quanta)  E = h  Planck’s Law) h = 6.63 x Js  E 3˝1 = h state 3 state 2 state 1 E

18 The Photoelectric Effect Light strikes metal surface and ejects an electron Classical physics predicts light intensity determines if e- is ejected. But e- is ejected only if light of minimum    is used; intensity does not matter. 7.1 h e-

19 The Photoelectric Effect

20 Einstein: Quantum Theory Explains the PE Effect Light is a stream of photons E photon >  E e- e- ejected with kinetic energy e-   E photon <  E e- e- not ejected   E e- e- in metal   E photon =  E e- e- ejected e-removed E photon = h

21 What is  ? (What is needed to eject e-?) How much E must the e- absorb if it moves from n=1 to n= oo ?  E e- = E e-,n= oo - E e-,n=1 This increase in E e- is supplied by the photon  E e- = E photon = h   or   =  E e- /h  E 1˝ oo = h  oo 1 E e-


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