phys 1260 exam 3 study questions and answers top graded 2024

electromagnetic waves - - light is the only thing we can see * originates from the accelerated motion of electrons * electromagnetic phenomenon - electromagnetic wave: made up of vibrating electric and magnetic fields if an electron vibrates up and down 1000 times each second, it generates an electromagnetic wave w/ a - frequency of 1000 Hz electromagnetic spectrum - - classification of electromagnetic eaves according to frequency - lowest frequency of visible light we can see appears red - highest frequency of visible light we can see appears violet - higher frequency of light is ultraviolet -> more energetic and causes sunburns - beyond are x-ray and gamma ray - no sharp boundary b/w regions the electromagnetic spectrum spans waves ranging from lowest to highest frequencies. the smallest portion of the electromagnetic spectrum is that of - visible light which of these is fundamentally different from the others? A. Sound waves B. light waves C. radio waves D. x-rays - Sound waves -> all are electromagnetic waves except sound which is a mechanical wave transparent materials - - light is transmitted similarly to sound * both are vibrations due to a vibrating source - how light penetrates transparent material such as glass: * electrons or molecules in the glass are forced into vibration * energy is momentarily absorbed and vibrates the electrons in the glass * this vibrating electron either emits a photon (a corpsucle of light) or transfers the energy as heat - time delay b/w absorption and re-emission of energy of vibrating electrons results in a lower average speed of light through a transparent material - in glass, infrared waves, w/ frequencies lower than those of visible light, cause not only the electrons but entire atoms or molecules to vibrate, increasing the temp of the structure - so we see that glass is transparent to visible light, but not ultraviolet and infrared light - avg speed of light through different materials * vacuum -- c (300,000,000 m/s) * atmosphere -- slightly less than c (but rounded off to c) * water -- 0.75 c * glass -- 0.67 c, depending on material * diamond -- 0.41 c strictly speaking, the photons of light incident on glass are - not the ones that travel through and exit the other side --> the light that exits the glass is not the same light that begins the process of absorption and re-emission compared w/ the frequency of illuminating light on a sheet of transparent plastic, the frequency of light that is transmitted - is the same --> speed of light in plastic may vary, but the frequency transmitted doesn't the avg speed of light is less in - glass opaque material - - most things around us are opaque --> they absorb light w/o re-emitting it * books, desks, chairs, and people are opaque