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