Physics
Posted on Apr 13, 2018 in Physics
//Light is a particle: Energy of Light is contained in small packets. bundles of energy=photons. Explains why light can travel through space. explains “Photoelectric Effect”>Energy from the light shining on a metal plate gives electrons in the metal enough energy escape. Bright light has more energy than dim light, but dim blue light can dislodge electrons while bright red light cannot. Low fre. light (red/orange) cannot eject electrons. High freq. light (blue/viol.) can eject electrons./Instead of light as individual particles, we think as rays. Shows detection of light. Rays (arrows) show the straight-line nature of light/ Waves come in mechanical&electromagnetic, can be longitudinal(particle and wave are parallel) or traverse(particle&wave are perpendicular)/Light is a Wave, behaves like waves! transverse, electromagnetic wave. Light reflects, diffracts, and refracts.//Wave – Particle Duality,light is a wave AND a particle,theorized in 1905, and all work since then has confirmed that light sometimes behaves like particles and sometimes like waves.//*EM Spectrum? Particles (electrons, photons, etc.) create changing E and B fields as they move. we can see EM waves!/warmer=more energy, colder=less energy./Light Moving,..Velocity or Speed can change depending on the situation. Speed of light is a fundamental constant. the speed of light depends upon the medium through which it travels. c = 3 x 108 m/s (300,000,000 m/s) ~ This can be substituted for v: c = d/t , c = f???? //Energy? A constant speed means as frequency increases, wavelength decreases. c = λ????, tied in to energy?: E = h???? , h = Planck’s Constant (6.626 x 10-34 Js)//Low Energy-Radio Waves (Microwaves) so small energy usually not reported./ New energy unit! Electron Volt (eV) 1 eV = 1.60218 x 10-19 j/Even with new unit, low energy lights contain smaller than 1 meV (10-3 eV)//Medium Energy=(Microwaves) Infrared, Visible (Ultraviolet), 0.001 eV to 10 eV (1.6 x 10-22 j to 1.6 x 10-18 j)// High Energy=(Ultraviolet) X-Rays and Gamma Rays Energies greater than 10 eV. AKA ionizing radiation; enough energy to rip electrons from atoms and molecules!//Effect of Mediums-Much like sound waves change in different mediums, so to does light! LIGHT travels fastest thru vacuum,//light travels slowest in diamond because the amount of refraction//Superposition of Light=Multiple waves interact with each other in superposition. Two waves in same space will add together. Above equilibrium (crest) = positive. Below equilibrium (trough) = negative. In reflection, diffraction, and refraction; it is the combination (superposition) of waves that results in what we see.//Resolving Light:Light coming from two sources will interact.// Reflection: Waves hit a boundary and bounce back.//Bubbles:multiple reflections interfering w each other(superposition)//Diffraction=waves hit a corner of a boundary&bend around(Young’s slit exp.), diffraction gratings produces rainbows->wavelength dependent! Some colors bend more than others. Longer wavelength, more it bends (diffracts).// Polarization-related to diffraction, only works bc of perpendicular nature of the electric magnetic fields of light. Pglasses=vertical.//Refraction:waves hit new medium&speed up or slow down. Light has bigger angle for faster.//Speed of Light: c = 3 x 108 m/s. Issa constant; it is also for light in a vacuum.//Mirages:waves can refract. Air behaves diff in diff air. Light travels faster in cold air. Inferior mirage=below what it should be, superior=above&reflected// Dispersion: refraction also wavelength dependent. Blue light refracts more than red light bc of WVL.. blue bends @ greater angle.// Rainbows: enters raindrops&refreacts back into our eyes at certain angle. Each particle reflects a diff light, mass raindrops=rainbow.//Fiber optic cable: waves can refract&reflect:Light follows liquid through bucket bc of total internal reflection. Light reflected asa hitting interface of air and liq. bc light goes through diff med at diff freq.//Shorter wvl, higher freq./longit=back and forth/elec spec travel same speed © but diff freq.)/violet has highest energy lvl/light ^ wvl V/evl ^, energy V/Transmitting=reflect,absorb,pass/pass completely=transparent/translucent (no pass) it is opaque, shield cuz block light.//Luminous-own souce, illuminous-reflects/black absorbs all color, white reflects all colors, blue reflects blue/lens have limited resolution/dispersion/rough=diffuse reflection/perpendicular to block/ Both send radio waves (invisible light) to cell towers. Phone calls take up more time and require long continuous waves of wavelengths. We use digital more cause short bursts are easier.
