Chapter 9 - Light Handout

Light Is light a wave or a particle? A WAVE (well, more on this later…). What is a wave, and what are the characteristics of waves, and how do waves differ from particles?? A WAVE IS A DISTURBANCE OF A MEDIUM. A WAVE TRANSPORTS ENERGY. A WAVE, UNLIKE A PARTICLE, HAS A WAVELENGTH, FREQUENCY, AND AMPLITUDE. A WAVE’S ENERGY DEPENDS ON ITS FREQUENCY (OR WAVELENGTH). MOST IMPORTANTLY, WAVES, UNLIKE PARTICLES, EXHIBIT INTERFERENCE EFFECTS. ALSO WAVES ARE SPREAD OUT, WHEREAS PARTICLES ARE LOCALIZED. What is the medium for light waves? ELECTROMAGNETIC FIELDS (NON-MATERIAL). What is electromagnetism? ELECTRICITY & MAGNETISM. What is the basis for electrical forces? CHARGED PARTICLES. What is the basis for magnetic forces? MOVING CHARGED PARTICLES. How are electricity and magnetism unified? ELECTRIC CURRENTS PRODUCE MAGNETISM. MAGNETISM PRODUCES ELECTRICAL CURRENTS. How does the planetary model of the atom account for electricity and magnetism? ELECTRICITY – CHARGED PARTICLES (ELECTRONS). MAGNETISM – MOVING ELECTRONS. Why do electrons orbit the nucleus? ELECTRICAL ATTRACTION BETWEEN NEGATIVELY CHARGED ELECTRON AND POSITIVELY CHARGED NUCLEUS. What is a force field? THE EFFECT THAT THE SOURCE OF THE FIELD HAS ON THE SURROUNDING SPACE. How is the field model an improvement over the “action-at-a-distance” model? IT AGREES WITH SPECIAL RELATIVITY. In terms of fields, how are electricity and magnetism unified? A CHANGING ELECTRIC FIELD PRODUCES A MAGNETIC FIELD, AND VICE VERSA. What is an electromagnetic wave? A DISTURBANCE OF AN ELECTROMAGNETIC FIELD. How fast does an electromagnetic wave travel? THE SPEED OF LIGHT = 300,000 KM/S. How is an electromagnetic wave generated? CHANGING ELECTRIC FIELD OR MAGNETIC FIELD, E.G., WIGGLING A CHARGED PARTICLE. How do electromagnetic waves differ, e.g., how are radio waves different from x-rays? How are they similar? THEY HAVE DIFFERENT WAVELENGTHS AND FREQUENCIES (AND THUS ENERGIES), BUT THEY ALL TRAVEL AT THE SPEED OF LIGHT. Keep going… IF YOU SHAKE A CHARGED PARTICLE A MILLION (106) TIMES A SECOND OR SO, A RADIO WAVE RESULTS. IF YOU SHAKE THE PARTICLE A HUNDRED BILLION BILLION (1020) TIMES A SECOND, A GAMMA RAY WILL BE PRODUCED. How about visible light? YOU MUST SHAKE THE CHARGED PARTICLE BETWEEN 4 AND 7.9 HUNDRED MILLION MILLION (1014) TIMES A SECOND! PRETTY SMALL RANGE!