1. 11/10/16
Today I will define the characteristics of a wave and compare the major regions of the electromagnetic spectrum.
Warm Up – What are the three types of energy we discussed in a previous chapter?

2. Chapter 4 – Electron Configuration
Part 1 - Waves

3. Radiant Energy
Light
Properties of both a particle and a wave!
We call this the dual nature of light

4. Nature of Light
Einstein proposed that: The particles or “packets” of light are called “PHOTONS”
Light travels in waves
We use four main terms to define the characteristics of these waves

5. Waves Wavelength (λ) units in meters (often nm)
distance between successive crests (high points) or troughs (low points)
units in meters (often nm)

6. Waves Amplitude (A) height of the wave (from origin to crest)
units in meters
Brightness of light

7. Waves Frequency () – how fast the wave is moving up and down
how many waves pass a fixed point in a given time
units in per seconds or Hertz (Hz)
Notice that the higher the frequency, the shorter the wavelength.

8. Wave Speed (c) – how fast light moves through space
All light (regardless of wavelength) moves through space at the speed of light!
c = 3.00 x 108 m/s

9. Electromagnetic Spectrum
Visible light is only one form of radiant energy.
7 Parts of the Electromagnetic Spectrum
Longest wavelength to Shortest:
Radio
Microwaves
Infrared
Visible Light
U.V. Light
X-Rays
Gamma-Rays

11. Homework
4-1 Review & Reinforcement (except #3)

12. 11/11/16
Today I will
determine the mathematical relationships in the electromagnetic spectrum
Warm up –
Draw a wave and label the origin, amplitude, wavelength, crest, and trough.
Now draw a wave with a larger frequency. Does it have a longer or shorter wavelength?

13. Wave Relationships
We said that wavelength and frequency are inversely related
When one goes up, the other goes down.

14. Wave Relationships Mathematical Relationship
Notice that speed of light is in m/s so…
FIRST!
Wavelength must be in meters and frequency must be hertz (/s)!

15. Wave Relationships For example: Wavelength is often given in nm.
You must convert first!
So 415 nm = ? m
1 m = 1x109nm

16. Wave Relationships
A helium-neon laser produces a red light whose wavelength is 633 nm. Calculate the frequency of the radiation.
 = 4.74 x 1014 Hz
Do you remember what to do when the variable is on the bottom???

17. Wave Relationships
What is the wavelength of U.V light that has a frequency of 4.50 x 1016 Hz?
Answer: 6.67 x m

18. Wave Relationships An interesting note: Radios broadcast using waves.
FM radio uses waves in the MHz range.
AM radio uses waves in the kHz range.

19. Wave Relationships
What is the wavelength of a radio wave that broadcasts at 600 AM?
600 AM = 600 kHz
Convert from kHz to Hz
Answer: 500 m
1 Hz = kHz

20. Homework
Wavelength & Frequency Calc

21. 11/14/16 Today I will Determine relationships between energy and waves
Solve for energy
Warm Up –
What is the frequency of light that has a wavelength of 245 nm?

22. Wave Relationships - energy
The higher the frequency, the more energy.

23. Wave Relationships - energy
Maxwell Plank
E=h
Where
E is energy
h is plank’s constant
 is frequency
Plank’s constant = x J·s
Energy and frequency are directly proportional
When one goes up, the other goes up!

24. Wave Relationships - energy
What is the energy of U.V. light with a frequency of 4.50 x Hz?
E = h 
E = (6.626 x 10 –34 Js)(4.50 x Hz)
E = 2.98 x 10 –17 J

25. Wave Relationships - energy
Determine the energy of light that has a wavelength of 450nm.
Do we know anything about wavelength and energy?
E=h

26. Wave Relationships - energy
Determine the energy of light that has a wavelength of 450nm.

27. Homework
Electromagnetic Radiation - Energy Calculations

28. 11/15/16
Today I will review the electromagnetic spectrum & calculations
Warm Up – How much energy is in a wave whose wavelength is 432 nm?

29. 11/16/16 Today I will explain the quantization of light
Warm Up – What is the relationship (in words) between:
Wavelength and frequency
Frequency and energy
Wavelength and energy

30. Quantization of Energy
Scientists were confused by the observation that the wavelength of the radiation changed with temperature

31. Quantization of Energy
Maxwell Planck – proposed that there are fixed amounts of energy that an object emits.
He called each of these pieces of energy a quantum.
Quantum means a fixed amount

32. Quantization of Energy
What is the difference between quantized and continuous?
Going up a ramp going up steps
If energy is in quanta, why aren’t we aware of it?
Quanta of energy are very, very small. Too small to notice.

33. Quantization of Energy
We have seen that not all light is the same.
We are surrounded by radio waves every day and they do not harm us, but gamma rays are very dangerous.
Very energetic light is dangerous (UV, X-rays, gamma)
Low frequency light does not have enough energy to be dangerous.

34. Photoelectric Effect
Electrons can be ejected from the surface of a metal when light shines on it.
Not all lights will cause this to happen on all metals.
For example. Red light is not able to release electrons from sodium, but violet light is.

35. Photoelectric Effect
Einstein proposed the idea of photons of light. Some photons have enough energy to release the electrons of a given metal and some do not.
One Quantum = One PHOTON
Compton
said that Light packets collide with the electrons to release them.
You can’t add the energy up as more light hits, so either a photon will release the electron or not.

36. Photoelectric cells
One everyday use of the photoelectric effect is photoelectric cells.
Automatic lights
Automatic doors
When the light shines, electrons are emitted and a current is produced. When that light is broken (by darkness or a body crossing it), the current is shut off and the desired effect is triggered.

37. Homework
4-2 Review & Reinforcement

38. 11/17/16 Objective – to describe the Bohr model of the atom
Warm Up – Which light will have a greater chance of producing the photoelectric effect: radio waves or ultraviolet waves? Why?

39. Bright Line spectra
Remember the idea that things changed colors when heated....
When certain salts are heated, they produce colorful light!

40. Bright Line spectra
These distinct colors are known as that element’s continuous spectrum
Lithium – red
Potassium – purplish pink
Sodium - yellow

41. Bright Line spectra Sometimes difficult to differentiate colors
When these lights are passed through a prism, they separate into distinct lines.
These combinations of lines are called line spectra
Bright Line spectra are unique to certain elements

42. Bohr Model
Neils Bohr – 1911
Wanted to explain line spectra
Electrons orbit the nucleus in defined energy levels
Gave each level a quantum number (n)

43. Bohr Model
When energy is absorbed, an electron can “jump” to a higher energy level
Energy absorbed

44. Bohr Model These electrons then “fall” back down and release energy.
This energy is released as light.

45. Bohr Model
Ground State- when an electron is on the energy level at which it normally resides
Excited State – when an electron is on a higher energy level than usual

46. Bohr Model Excited state Ground state
Energy absorbed
Ground state
Energy released as light
In this example, n=1 is the ground state and n=2 is the excited state

47. Bohr Model

49. Bohr Model
The amount of energy released is determined by how that atom’s electrons jump and fall.
The wavelengths (or colors) of light are determined by those energies!

50. Bohr Model
Bohr’s model and the calculations of energy and wavelength work very well for Hydrogen.
However, with larger atoms, the model works only approximately.
Ultimately, this model does not work, but it was a good starting point for scientists, especially in thinking of distinct energy levels!

51. Today I will review chapter 4 (part 1)
11/18/16
Today I will review chapter 4 (part 1)
Warm Up
If light has an energy of 1.2 x J, what is its wavelength?
c = 3.00 x 108 m/s h=6.626 x J·s

52. Homework
Chapter 4 Review

53. 11/21/16 Today I will prepare for the chapter 4 (part 1) test
Warm Up – Explain the dual nature of light.