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

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

Waves, Light, Quantum

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

Other Periodic Trends

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

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

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

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

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

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

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

 = c/ = ( 3.00 x 10 8 m/s) / 4.69 x 10 14 Hz = 6.40 x 10 -7 m Problem 4: A laser used to weld detached retinas produces light with frequency of 4.69 x 10 14 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)

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)

Planck’s Quantum Theory

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

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

Planck’s Basic Ideas Energy is emitted or absorbed in discrete units (quanta)  E = h  Planck’s Law) h = 6.63 x 10 -34 Js  E 3˝1 = h state 3 state 2 state 1 E

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-

The Photoelectric Effect

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

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-

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

Similar presentations