1. Light and Quantized Energy

2. Learning Objectives Compare the wave and particle nature of light.
Contrast continuous electromagnetic spectra and atomic emission spectra.
Explain why atoms of a particular element give off specific wavelengths of light when their electrons are excited.

3. Light and Quantized Energy
Light, a form of electromagnetic radiation, has characteristics of both a wave and a particle.
Light exhibits wavelike behavior as it travels through space.
Light exhibits particle like behavior as it interacts with matter.
- The Original Double Slit Experiment (light as a wave)
- What Can Frogs See That We Can't? (light as a particle)
- Single Photon Interference

4. The Wave Nature of Light
Visible light is a type of electromagnetic radiation-a form of energy that exhibits wavelike behavior as it travels through space. Examples: microwaves, x-rays, radio waves
--cool one
Is light a particle or a wave? - Colm Kelleher
Quantum Theory - Full Documentary HD -

5. Characteristics of Waves
The wavelength (represented by λ, the Greek letter lambda) is the shortest distance between equivalent points on a continuous wave.
The frequency (represented by ν, the Greek letter nu) is the number of waves that pass a given point per second.
The amplitude of a wave is the wave’s height.
Quick Demo – Wave characteristics

6. Characteristics of Waves
All electromagnetic waves, including visible light, travel at the speed of light.
Electromagnetic Wave Relationship: c = λν
c = speed of light, a constant (3.00 x 108 m/s)
ν= frequency
λ = wavelength

7. Electromagnetic Spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.

8. Continuous Spectrum
A continuous spectrum is an emission spectrum that exhibits all the wavelengths or frequencies of visible light (violet to red).
White light contains a nearly continuous range of wavelengths and frequencies.
White light passing through a prism separates into a continuous spectrum of colors.
These are the colors of the visible spectrum. The spectrum is called continuous because each point of it corresponds to a unique wavelength and frequency.

9. The Particle Nature of Light
Max Planck studied the light emitted by heated objects.
His conclusion: matter can gain or lose energy only in small, specific amounts called quanta.
A quantum is the minimum amount of energy that can be gained or lost by an atom.
A photon is a particle of light with a particular frequency.
When objects are heated, they emit glowing light. A piece of iron appears dark gray at room temperature, glows red when heated sufficiently, and turns orange, then bluish in color at even higher temperatures. These different colors correspond to different frequencies and wavelengths.
The wave model could not explain the emission of these different wavelengths. Max Planck began searching for an explanation of this phenomenon as he studied light emitted by heated objects. His study led him to the conclusion that matter can gain or lose energy only in small, specific amounts called quanta.
As an object becomes hotter, it emits light at higher frequencies, and therefore of different colors.

10. The Particle Nature of Light
A relationship between the energy of a quantum and the frequency of the emitted radiation
Relationship between energy and freqency E = hν
E = Energy,
h = Planck’s constant ( x Js)
ν = frequency,
The equation shows that the energy of radiation and the radiation’s frequency are directly proportional.

11. Light’s Dual Nature
The energy of a photon of light is directly proportional to its frequency.
Energy ↑ Frequency ↑
Energy ↓ Frequency ↓
Energy and frequency are inversely proportional to wavelength.
energy/frequency ↑ Wavelength ↓
energy/frequency ↓ Wavelength ↑
Long wavelength = low frequency = low energy
Short wavelength = high frequency = high energy

12. Learning Check
List the following in order of increasing wavelength: microwaves, ultraviolet (UV), gamma (γ), x-rays

13. Learning Check
List the following in order of increasing energy: microwaves, ultraviolet (UV), gamma (γ), x-rays

14. Learning Check
What color of visible light has the longest wavelength?

15. Learning Check
What color of visible light has the highest energy?

16. Bohr Model
Suggested that electrons orbit the nucleus in fixed energy levels (or shells)
Electrons could jump between levels, giving off light we can see

17. Bohr’s Model of the Atom
Electron transitions involve jumps of definite amounts of energy.
This produces bands of light with definite wavelengths.

18. Energy States of Atoms
The lowest allowable energy state of an atom is called its ground state.
When an atom gains energy, it is said to be in an excited state.
Various possibilities of excited states create characteristic spectral emissions.

19. Atomic Emission Spectra
The atomic emission spectrum or line spectrum of an element is the set of frequencies of the electromagnetic waves emitted by atoms of a specific element.

20. Continuous vs Line Spectrum

21. Atomic Emission Spectra
Like a fingerprint, each element’s atomic emission spectrum is unique and can be used to identify an element

22. Summary
All waves are defined by their wavelengths, frequencies, amplitudes, and speeds.
In a vacuum, all electromagnetic waves travel at the speed of light.
Electromagnetic radiation has both wave and particle properties.
Matter emits and absorbs energy in quanta.
White light produces a continuous spectrum.
An element’s emission spectrum consists of a series of lines of individual colors.

23. AllWrite RoundRobin
All team members look at notes on page 108 and think of one potential test question and write it down on your white board.
Starting with TM#____ take turns sharing the question you came up with.
Team agrees on questions to write down.
All team members record questions.
Repeat until there are 3-4 questions per page of notes.

24. Summaries
When your team has finished recording the cue column questions, work on your summaries.

25. Title page 112, Electromagnetic Spectrum
Cut out and glue the electromagnetic spectrum to page 112.

26. Title page 113 Electromagnetic Spectrum Questions
Cut out and glue the Electromagnetic Spectrum questions to page 113.

27. Flame Demo I am going to light five different metal salts on fire.
Record the names of each metal salt and your observations for each in your science notebook.

28. Title page 114 Flame Demo
Metal Salt
Flame Color

29. Write the following question under your data table.
Question: Why did we only see one color for each metallic salt rather than the colors that would be present in a line spectra for each element?
If you weren’t here the day of the demo, use the slides to complete your data table and then answer the question.

30. LiCl – Lithium Chloride SrCl2 – strontium chloride
Flame Demo
LiCl – Lithium Chloride
SrCl2 – strontium chloride

31. KCl – potassium chloride CuCl2 – copper II chloride
Flame Demo
KCl – potassium chloride
CuCl2 – copper II chloride

32. Flame Demo
BaCl2 – barium chloride

33. Spectrometer
A spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light  over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis  to identify materials.