1. Physics and the Quantum Mechanical Model

2. Light (Waves) Amplitude – The waves height from zero to the crest
Wavelength (λ) – The distance between two crests.
Frequency (ν) – The number of waves that pass a given point per unit time. Usually expressed in Hertz (Hz), cycles per second (s-1).

3. Light Waves (Continued)
The product of frequency and wavelength always equals a constant (c), the speed of light (2.998 x 108 m/s )
What type of relationship does wavelength and frequency have? (hint: linear, inverse, or quadratic)
Inverse. If we rearrange the formula to solve for wavelength, we get the following equation:
λ = c / ν
What happens to wavelength as frequency increases?
Wavelength decreases

4. Sample Problem
What is the wavelength of radiation with a frequency of 1.50 X 1013 Hz? Does this radiation have a longer or shorter wavelength than red light? (Red light λ = 10-6)
λ = c / ν
λ = X 108 m/s / 1.50 X 1013 Hz
λ = 2.0 X 10-5 m
The radiation has a longer wavelength than red light.

5. Light Waves (Continued)
Light consists of electromagnetic waves
Names a few types of electromagnetic radiation:
Radio waves, microwaves, infrared waves, visible light, ultraviolet waves. X-rays, and gamma rays.
All electromagnetic waves travel in a vacuum at a speed of X 108 m/s  speed of light

6. Light Waves (Continued)
What happens when sunlight passes through a prism?
Different frequencies separate into a spectrum of colors. (Atomic emission spectrum)
Name a natural phenomenon where light get separated into its constituent spectrum of colors.
A rainbow

7. Atomic Spectra
Passing an electric current through a gas in a neon tube energizes the electrons of the atoms of gas, and causes them to emit light.
When atoms absorb energy, electrons move to higher energy levels, and these electrons lose energy by emitting light when they return to lower energy levels.

8. Atomic Spectra Explanation
Ground state - The lowest possible energy level of an electron. Here the principal quantum number (n) is 1.
Excitation of an electron raises it from the ground state to an excited state (n) = 2,3,4,5,etc…
The light emitted by the electron moving from a higher to a lower energy level has a frequency directly proportional to the energy of the electron

9. Quantum Mechanics
Describes the motions of subatomic particles and atoms as waves.
Light quanta – Photon
Heisenberg uncertainty principal – It is impossible to know exactly both the velocity and the position of a particle at the same time.