1. Light Diffraction and How CDs Work
PEOPLE Program
Light Diffraction and How CDs Work

2. How do Computers and CDs Store Numbers
Computers are constructed of digital electronics => two states: “on” “off”
Binary number system consists of 0 and 1 only
On-off patterns are used to encode numbers using binary number system
Most computer electronics
Voltage levels
CD-ROM
Microscopic bumps on disk surface
Hard disk
Magnetism
Computer memory
Electric charges on capacitors

3. Evolution of discs Turn to handouts: how to measure it?
Microscope: not easy to find a microscope to get enough resolution. MB
4.7 GB
15 GB
25 GB
Ronchi Ruling: 1.88 μm
Narrower tracks, higher storage density!

4. How does diffraction work?
nλ = dsinθ
d = spacing of grating
(or spacing between the tracks for CDs)