Light It is against the honor code to “click” for someone else- violators will loose all clicker pts. We have observed light HITT RF Remote Login Procedure: 1. travels in straight lines The radio channel number for this room is “09” (zero, nine). 2. reflects It is STRONGLY recommended to login your remote for every class just 3. refracts to be sure it is on the correct radio channel and working before class. 1. PRESS AND HOLD THE DOWN ARROW KEY until the It also GREEN light on the remote turns RED. 4. transmits energy from 2. PRESS THE “0” KEY and you will see the RED light flash one place to another GREEN. 3. PRESS THE “9” KEY and you will see the RED light flash Two theories could explain GREEN. these phenomena. 4. PRESS AND RELEASE THE DOWN ARROW KEY again and you will see the red light search for the receiver, if it BLINKS GREEN MULTIPLE TIMES you are logged in. Thanks to friends at Texas A&M U for help with the slides What were the two theories of light in the 1600s and who were their main advocates? The WAVE THEORY, advocated by Christian Huygens • A. Corpuscular-Newton and Wave-Huygens and Robert Hooke, • B. Corpuscular-Huygens and Wave-Newton said that light was a wave. • C. Gravity-Newton and String-Weinberg The PARTICLE (corpuscular) THEORY, advocated • D. Force-Newton and Wave-Huygens by Isaac Newton and later by Pierre Laplace, said • E. Wave-Aristotle and Gravity-Newton that light was made up of a stream of tiny particles called corpuscles. The more popular theory was the particle theory The debate among the two sides continued because of the reputation of Isaac Newton.. through the mid 1800’s. Newton’s particle theory could easily explain the 1801 interference of light was discovered straight line travel of light, reflection, and energy 1816 - diffraction of light (actually observed transmission, but had trouble explaining refraction. in the 1600’s but not given much significance) was explained using interference principles Newton’s explanation of refraction required that light must travel faster in water than in air. Neither phenomena could be explained satisfactorily by the particle theory. Huygen’s wave theory could easily explain reflection, energy transmission, and refraction, but had difficulty The final blow to the particle explaining the straight line travel of light. theory came in 1850 when The wave theory’s explanation of refraction Jean Foucault discovered that required that light must travel light traveled faster in air slower in water than in air. than in water. It was then widely accepted that light was a wave, but what kind of wave? In 1865, James Maxwell developed ideas began by Michael Faraday into a series of equations that proposed the electromagnetic wave theory. It said that light was a type of e/m wave: a periodic foucault light demo disturbance involving electric and magnetic forces. In 1885, Heinrich Hertz Foucault put a tube of water in the light beam and experimentally confirmed showed that light slowed down in the water! the e/m theory of light. Newton was wrong! The whole universe is composed of SHOs Oscillators make Waves SHO is system with linear restoring force to original All waves carry energy and momentum shape/position Types of Waves – Transverse Each part of spring moves Mass/spring Pendulum To wave motion Like AM radio 1 k g Frequency f = T2 ms m p L X direction (space/not time) Longitudinal or compression wave Wave motion-Wave velocity c c c t c = λƒ Always true: Light-transverse Sound-longitudinal Any wave Most waves need a medium-- Except light.