# The Electromagnetic Spectrum & Electromagnetic Radiation

## Presentation on theme: "The Electromagnetic Spectrum & Electromagnetic Radiation"— Presentation transcript:

The Electromagnetic Spectrum & Electromagnetic Radiation

What are electromagnetic waves?
Produced by the motion of electrically charged particles Also called “electromagnetic radiation” because they radiate from electrically charged particles.

LIGHT According to the wave theory, light consists of electromagnetic waves Examples of electromagnetic radiation include: Radiowaves Microwaves Infrared waves Visible light Ultraviolet light X-rays Gamma rays

This is the electromagnetic spectrum
R O Y G B I V

Properties of waves Wavelength Frequency Amplitude
Cycles / second (Hertz)

Wavelength Shows a long wavelength Shows a short wavelength
Measured from crest to crest Symbol =

Frequency The number of wave cycles in a given time, measured in hertz (Hz)

Amplitude The wave’s height

The Visible Spectrum ROYGBIV Red: longer wavelength, lower frequency
Violet: shorter wavelength, higher frequency

Electromagnetic waves we can’t see
Microwaves Radio waves X-Rays Ultraviolet Rays Gamma Rays

How do we get these?

Those shiny electrons! Electrons can change energy levels

When energy is added to an electron, it goes to a higher energy level
Eventually the electron needs to return to it’s ground state. When it does, energy is released in the form of light.

Atomic Spectra

The energy change of the electron gives off light with a specific frequency
If an electron falls to energy level 1, ultraviolet light is emitted If an electron falls to energy level 2, visible light is emitted If an electron falls to energy level 3, infrared light is emitted

Spectra for every element!

What’s happening? When heated, electrons enter an energized state.
Eventually, excess energy is released as a photon of light. High energy photons correspond to short wavelength light Low energy photons produce long wavelength light The colors of the light (or flame) correspond to electrons of specific energies

Remember, a Quantum is. . . The amount of energy needed for an electron to change energy levels

Draw it!

The Importance of the Atomic Emission Spectrum
Like a fingerprint for the element Each element has a unique number of electrons So the electrons move to different energy levels when they absorb energy. When the electrons fall, they produce a spectra specific to that element

So, the atomic spectra can be used to identify elements!

Dual Personality So far, we’ve been talking about the wave theory of light. Einstein said that electromagnetic radiation acts like a wave AND like particles (photons)

A packet of energy that behaves like both a particle AND a wave
A Photon A packet of energy that behaves like both a particle AND a wave

de Broglie found (with math) that particles DO behave as waves.
A golf ball, when hit, has a wavelength as it travels through the air, though very small To observe their wavelength, particles must be very small

Because of Bohr and Einstein and de Broglie
Scientists say there is a Wave-Particle Duality of Light

Not Just Light This applies to all things, but it’s easier to observe in small ones

Heisenberg’s Uncertainty Principle
Heisenberg said that it’s impossible to know both the location and the velocity of a particle at the same time