Unit 6 – Lecture 2

EM Waves do not require a medium work by vibrating electric & magnetic fields

Electromagnetic Spectrum

The Electromagnetic Spectrum Radio Waves – carry information radios am fm televisions MRI cell phones & cell phone towers

The Electromagnetic Spectrum Microwaves microwave oven Doppler radar [weather detection] other radar

The Electromagnetic Spectrum Infrared heat [thermal energy] remote controls heating lamps for food

The Electromagnetic Spectrum Infrared picked up by night vision goggles thermal imagery some animals can see in infrared [rattlesnakes]

The Electromagnetic Spectrum Visible Light light bulb…etc. a prism –  separates “white “ light into its colors

The Electromagnetic Spectrum Ultraviolet UV waves from sun and other stars helps us make vitamin D kill bacteria on food [damage cells] fluorescent materials glow [black light] can be seen by some animals [birds, bees]

The Electromagnetic Spectrum X-rays medical appliations airport screening

The Electromagnetic Spectrum Gamma Rays radioactive [unit 3!] E emitted from nucleus medical applications radiation therapy sterilization used to look at stars

X-Rays

Sound Important Sound Terms: Decibel – unit of sound intensity Ultrasonic – above 20,000 hertz Echolocation – using reflected waves to judge the size, shape, or location of an object Supersonic – faster than the speed of sound Vibration – cause of sound

Sound caused by vibrations composed of compressional waves in turn this vibrates your ear drum to send signals to your brain waves must have a medium through which to travel

Sound

speed of sound is determined by the medium through which it travels type of medium state of matter solids, liquids, gases closer the particles, faster the travel of sound temperature of the medium increased temperature, increased sound this change of speed distorts the sound

The Doppler Effect the change in pitch and frequency due to a moving wave source reason why the same thing sounds different as it approaches you or moves farther away higher as approaching lower as moving away

The Doppler Effect basically… imagine you’re throwing cheese-balls at someone at regular intervals. [constant frequency] if you stay in the same place, each ball hits your victim at the same interval [frequency] at which you’re throwing it.

The Doppler Effect basically… now, if you start running toward your victim, the distance between you and the person keeps getting smaller because the distance is smaller, the cheese-balls are hitting the victim more quickly [with a higher frequency] this is why the pitch gets higher as the object approaches.

The Doppler Effect basically… …but to you, the frequency is the same this is how the sound seems to the person who’s in the car. [it remains the same]

The Doppler Effect basically… as you run, you keep throwing the cheese-balls at the same frequency …but as you get further, it takes more time for each cheese- ball to reach your victim. they are being pelted with cheese-balls less often [lower frequency] this is why the pitch gets lower as the object moves farther away

The Doppler Effect In the story… what represented the frequency? what represented the sound waves? What would display the doppler effect moreso: a race car passing a police siren

Speed Equations Speed of Sound speed = distance / time v = d / t Speed of Waves speed = wavelength * frequency v = λ * f

Homework New worksheet – Speed of Sound Problems ALSO – work on your packet unless it’s finished because it’s finished you’re willing to show it to me and turn it in for collection early.