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**Light and Quantized Energy**

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Fireworks Video As you watch this video, answer the questions on your notes page.

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**Electromagnetic Radiation**

A form of energy that exhibits wavelike behavior as it travels through space Examples: Visible light, microwaves, x-rays, radio and television waves Different forms of electromagnetic radiation can be seen on the electromagnetic spectrum

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**Electromagnetic Spectrum**

Encompasses all forms of electromagnetic radiation, showing the differences of wavelength and frequency in the types of radiation

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**Electromagnetic Spectrum**

Increasing Frequency Decreasing Wavelength

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**Characteristics of Waves**

Wavelength ( λ ) – shortest distance between 2 equivalent points on a continuous waves (from crest to crest or from trough to trough) Units of wavelength: Usually in meters, centimeters or nanometers

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**Comparing Wavelengths**

Which wave has a longer wavelength? Which wave has the shorter wavelength? long wavelength crest Wavelength Wavelength trough short wavelength

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**Characteristics of Waves**

Frequency ( v ) – number of waves that pass a given point per second Units of frequency: waves per second 1 / s = s -1 = Hertz

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**Another way to look at Frequency**

These 2 waves are traveling at = speeds… more crests cross the ‘finish line’ in a matter of one min.? which wave will have low frequency = long wavelength high frequency = short wavelength

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**Characteristics of a Wave**

Amplitude – wave’s height from the origin of the wave to the crest or from the origin to the trough origin

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Parts of a wave Label wavelength, peak, trough and amplitude on the following wave: peak wavelength amplitude trough

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Picking back up Electromagnetic radiation - a form of energy that exhibits wavelike behavior as it travels through space Electromagnetic Spectrum - Encompasses all forms of electromagnetic radiation, showing the differences of wavelength and frequency in the types of radiation Wavelength ( λ ) – shortest distance between 2 equivalent points on a continuous waves Frequency ( v ) – number of waves that pass a given point per second Amplitude – wave’s height from the origin of the wave to the crest or from the origin to the trough

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**Let’s Practice! Study Guide page 25, #1-8. Energy Wave Light Speed**

Wavelength Amplitude Frequency Hertz

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**Can we do some more? Yes, we can!**

Page 25, questions 9-11. A and C B 2 hertz

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Wave Calculations All electromagnetic waves travel at the speed of light in a vacuum Speed of light (c) = 3.00 x 108 m/s Speed of light is equal to product of wavelength and frequency c = λ v

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**To solve for…. To solve for wavelength: λ = c / v**

To solve for frequency: v = c / λ

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**Wave Calculations Practice**

Calculate the υ of a wave that has a wavelength of 5.00 x 10-6 m. ν c = λ ν 3.00 x 108 m/sec 5.00 x m = = 6.00 x Hz ν What is the λ of radiation with a frequency of 1.50 x 1013 Hz? c λ = ν λ = 3.00 x m/sec 1.50 x Hz λ = 2.00 x m

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**Emissions of light by atoms**

all elements will emit light when excited (i.e. by electricity). atoms absorb energy and then emit an equal amount of energy in the form of electromagnetic radiation (i.e. light). - atoms emit a characteristic wavelength - Ne = orange - red - Na = bright yellow if we pass this light through a prism (separate the λ) we get an atomic emission spectrum. ex. of wavelengths emitted

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**Atomic Emission vs. Continuous**

emission spectra are unique to particular elements. only show certain lines of the continuous spectrum (white light). have helped us gather a lot of info. about our universe! atomic absorption spectra shows colors missing from the continuous spectrum (missing λ were absorbed by the element). continuous absorption emission

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**Atomic Emission Spectrum**

The set of frequencies of the electromagnetic waves emitted by atoms of the element Consists of several lines of color and not a continuous range

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Time to Practice Page 26, #16-22. False True

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Quantum of Energy e- are found on certain energy levels (orbitals) around the atom. there is a maximum of seven energy levels in an atom. e- on the energy level closest to the nucleus have the lowest energy. The 7th energy level has the highest energy. - An e- requires one ‘quanta’ (minimum amount of energy gained or lost by an electron) of energy to jump to the next energy level.

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**e- at their lowest energy level are considered to be at the**

ground state (most stable). if e- absorb a quantum or more of energy (from electricity), they can jump to higher energy levels (excited state). e- must lose energy in order to fall from the excited state back to the ground state. - this energy is emitted in the form of electromagnetic radiation (sometimes visible)!

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**Energy Levels Principal quantum number =**

= Electrons = Protons = Neutrons If there are seven energy levels possible, do you think you can tell how many energy levels there would be in at atom based on looking at the periodic table? Principal quantum number = Period number on periodic table

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