Interference Applications:

1. Anti-reflection coatings (cameras, glasses): Thin film with $t = \lambda/(4n)$ causes destructive interference of reflected light
2. Soap films and oil slicks: Color patterns due to thin film interference (amplitude division)
3. Newton's rings: Used to test flatness of optical surfaces; circular fringes indicate spherical lens profile
4. Michelson interferometer: Used to detect gravitational waves (LIGO), measure lengths to nanometer precision

Diffraction Applications:

1. X-ray crystallography: Diffraction of X-rays by crystal planes determines atomic structure
2. Optical gratings: Multiple slits for precise wavelength measurement (spectroscopy)
3. CD/DVD reading: Laser diffraction from track patterns reads data

Polarization Applications:

1. Polaroid sunglasses: Block horizontally polarized glare from reflective surfaces
2. LCD screens: Liquid crystal cells rotate polarization to control pixel brightness
3. 3D cinema: Left and right eye images have perpendicular polarizations
4. Photography: Polarizing filters remove glare, enhance sky contrast
5. Saccharimetry: Measuring sugar concentration by optical rotation