Wave Characteristics 8 boxes needed
Heat Review • How does the heat travel to my hand? • Which spoon is a better insulator? • What does that mean in terms of specific heat?
Conduction When you heat a metal strip at one end, the heat travels to the other end through conduction. As you heat the metal, the particles VIBRATE, these VIBRATIONS make the adjacent particles VIBRATE, and so on and so on, the VIBRATIONS are passed along the metal and so is the heat.
How do these molecules move? Cools at the surface Convection current Hot water rises Cooler water sinks
Convection AND Conduction Box #1-2 notes • Molecules (ingredients) in solids, liquids, and gases travel by vibrations. • Whether you heat up a solid (spoon) or liquid (water), the particles VIBRATE, these VIBRATIONS make the adjacent particles VIBRATE, and so on and so on. • The faster the vibrations, the more kinetic energy the object is said to have.
Good Vibrations Box #2- 2 notes • All around us we see things that vibrate • Even things too small to see, such as atoms, are constantly wiggling and vibrating • Vibration: repeated back and forth motion • Vibrations cause waves. Waves are propagations of vibrations throughout space. • Wave: a wiggle/vibration in time and space
Wave Motion • A periodic disturbance which travels through a medium from one point in space to the others are what we call waves. • Wave motion appears in almost every branch of Physics.
A wave travels a certain distance before it starts to repeat. • The distance between two corresponding parts of a wave is its wavelength.
Wavelength Box #3 • Wavelength, l, is the distance between two consecutive peaks (m).
Parts of a Wavelength • Wavelength can be measured either from crest to crest or trough to trough • Crest: like a water wave, High point of a wave • Trough: Low point of a wave
Parts of a Wavelength Box #4-2 notes and drawing • Crest: High point of a wave • Trough: Low point of a wave
Amplitude Box #5-2 notes • Amplitude is the height of the wave above or below the equilibrium point.
Amplitude is the maximum distance a medium (object) moves up or down from its rest position. • The more energy an object has, the greater its amplitude. Box #5 Continued
Frequency Box #6-2 notes • Frequency, f, is the number of waves passing a particular point in one second. • The frequency of a wave is called the hertz (Hz)
If you don’t go to class FREQUENTLY…it HERTZ your grade! • A wave that occurs every second has a frequency of 1 wave per second (1/s) or 1 Hz. • If two waves pass every second the frequency is 2 waves per second (2/s) or 2 Hz.
Which picture shows Low frequency Wave? High Frequency Low Frequency
What is the difference in the sound waves below? • Frequency? Amplitude? • The sound waves are exhibiting the same frequency but different amplitudes
Check Your Understanding so far… • A surfer wishing to ride a big wave is most interested in a wave’s- • Amplitude
Check Your Understanding… • Which property describes how often a wave occurs? Amplitude Wavelength Frequency
Wave Speed • Different waves travel at different speeds. • Think about watching a distant thunderstorm on a hot summer day. • The thunder occurs the instant the lightning flashes, but the light and sound reaches you seconds apart. • This happens because light waves travel much faster than sound waves. • In fact, light waves travel about a million times faster than sound waves.
Do you remember? • What do you need in order to calculate speed? • Distance and time • Wave speed is calculated the same way • With waves, distance=wavelength and time=frequency
Wave Speed Box #7 • Velocity of a Wave=frequency x wavelength (m/s) (Hz) (m)
Problem #1 • What is the speed of a wave with a frequency of 0.2 Hz and a wavelength of 100 meters?
Problem #2 • A tuning fork has a frequency of 280 hertz, and the wavelength of the sound produced is 1.5 meters. Calculate the velocity of the wave.
Problem #3 • If the ocean waves have a frequency of 0.042 Hz, what is the speed of the boat as it travels 267 m?
Problem #4 • A wave is moving toward shore with a velocity of 5.0 m/s. If its frequency is 2.5 hertz, what is its wavelength?
Problem #5 • Observing an approaching thunderstorm and using a stopwatch, a student finds that it takes 8.40 seconds for thunder to be heard after a lightning bolt strikes. The student has learned that it takes 3 seconds for sound to travel 1000 m. How far away is the storm?
Problem #6 • The time required for a laser pulse to travel to an object and back again can be used to determine how far away the object is. If a laser pulse takes 3.30 x 10-6 s to travel to an object and back, how far away is the object from the source of the laser pulse?
http://micro.magnet.fsu.edu/primer/java/wavebasics/index.htmlhttp://micro.magnet.fsu.edu/primer/java/wavebasics/index.html Box #8 • As the frequency of a wave increases, the wavelength • Amplitude ____________ have any effect on wave speed, frequency, or wavelength. decreases- inverse relationship. does not
Another interactive website is at: http://glencoe.mcgraw-hill.com/sites/0078779626/student_view0/unit3/chapter10/virtual_lab.html