1. Physics and the Quantum Mechanical Model Section 13.3
KEY TERMS:
Amplitude
Wavelength
Frequency
Electromagnetic Spectrum
Emission Spectrum
Photoelectric Effect
Ground State

2. Key Concepts
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

3. Light and Atomic Spectra

4. Electromagnetic Spectrum and how wavelength relates to various objects

5. Speed of light = wavelength x frequency c = λ ν
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 cycle
Units = 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

6. Electromagnetic Spectrum – various colors you see due to the wavelength of light
Emission Spectrum – line of color that correlates to one exact frequency

7. Photoelectric effect 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

8. Photoelectric Effect 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
Electrons being ejected
Light energy
metal

9. Application of photoelectric effect:
Application of photoelectric effect: Photoelectric cells uses the energy of light to generate electricity for homes, vehicles, etc

10. Atomic Spectra 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

11. Quantum Mechanics
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