Light as a Wave The EM Spectrum, Diffraction, Interactions with Matter, and Young’s Double Slit Experiment
Light is a Wave • Reflects • Refracts • Diffracts • Interferes • Is Absorbed
The EM Spectrum • Regions with longer wavelengths have greater ability to diffract • Regions with high frequencies • Behave more like particles only • Can cause great damage to living things
Visible Light • White light forms the continuous spectrum of visible light • Visible Spectrum made up of all colors • Colors have different wavelengths • red has longest wavelength (700 nm) • violet the smallest (400 nm) • (1 nm = 0.000000001 m) • If the spectrum was scaled to 2000 miles, visible light would only be one inch of it
Wavelength vs Frequency • If red has the longest wavelength, and violet has the shortest, which has the greater velocity? • Neither - Trick question! Both are light, so both travel at the speed of light! But…. • Which has the highest frequency? • Yep, violet!
Interference can be demonstrated with light through Young’s Double Slit Experiment. Proves light particles can behave like waves.
Matter and Light • Luminous objects emit light • Incandescent, fluorescent bulbs, neonlight, “black” light, laser light • Because of excited atoms • Illuminated objects are objects that are reflecting light produced by another source. • The moon is illuminated by the sun • A white projector screen is illuminated by the projector
Matter and Light • Transparent objects transmit light easily • Air, glass • Light entering/exiting a medium changes its speed • There can be scattering (blue sky) and/or refraction (prism) • Opaque objects (non-luminous) do not emit or transmit light, instead they: • reflect • absorb