KEY TERMS:◦ Amplitude◦ Wavelength◦ Frequency◦ Electromagnetic Spectrum◦ Emission Spectrum◦ Photoelectric Effect◦ Ground State

The product of frequency (ν) and wavelength (λ) always equals the speed of light (c) c = λ ν

Line emission spectra illustrate the amount of quantized energy levels

De Broglie proposed that all matter in motion has wavelength properties

Photoelectric Effect – metals eject electrons called photoelectrons when light shines on them◦ Only certain frequencies of light will demonstrate the

photoelectric effect

Electromagnetic Spectrum and how wavelength relates to various objects

Frequency = number of complete waves per unit of time Units = Hertz (Hz) or per second (sec-1)

Amplitude = wave’s height from the origin

Wavelength = The length of one complete wave cycleUnits = Ǻ, nm, cm, m

• Wavelength (λ) and Frequency (ν) are inversely related• Speed of light = wavelength x frequency

• c = λ ν• As wavelength increases, frequency decreases

Electromagnetic Spectrum – various colors you see due to the wavelength of light

Emission Spectrum – line of color that correlates to one exact frequency

Max Planck studied this concept◦ Trying to describe why iron (or metals in general)

changed color when heated ◦ Energy of a quantum = Planck’s constant x

frequency E = h ν

◦ The size of the quantum being absorbed or emitted depends on the size of the energy change Small energy change = low frequency radiation Large energy change = high frequency radiation

Albert Einstein ◦ Proposed that light can be described as quanta of

energy that behave as if they were particles◦ Photons = light energy◦ Metals eject electrons when specific wavelengths

of light shines on them

Light energy

metal

Electrons being ejected

Electrons absorb energy and get “excited”

When they are excited, they jump up to a new energy level (farther away from nucleus)

The electron then loses that energy and falls back down to ground state

The energy emitted produces the various colors of light that you see

If light behaves as waves and particles, can particles behave as waves?◦ Question proposed by De Broglie (French

graduate student)◦ All matter exhibits wavelike motions◦ Particles gain or lose energy in packages called

quanta◦ Heisenberg uncertainty principle

It is impossible to know exactly both the velocity and position of a particle at the same time