Waves And Wave Characteristics Wave A periodic disturbance
Waves And Wave Characteristics
Wave A periodic disturbance that transfers energy through a medium (substance) or field
Pulse A single disturbance that transfers energy
Two types of waves 1) Mechanical – particles in a substance that move periodically - require a medium to travel through Ex: water spring sound The Wave
Two types of waves 2) Electromagnetic– combination of electric and magnetic fields that - does NOT require a medium to travel through, can move through a vacuum Ex: light radio x-rays
Two types of wave propagation 1) Transverse – particles move perpendicular to the direction of wave travel Ex: light s-waves The Wave
Two types of waves 2) Longitudinal – particles move parallel to the direction of wave travel Ex: sound p-waves
Wave characteristics 1) Amplitude – the maximum displacement of a particle from its equilibrium position The height of a crest of the depth of a trough Related to the amount of energy it is carrying Sound – volume Light - brightness
2) Wavelength – the length of a wave Symbol – l Unit - m
3) Phase – points on a wave that are in phase are at the same place on the wave - the distance between two points that are in phase is one wavelength (or a multiple)
4) Period – time for one complete oscillation to occur Unit – s Symbol – T
5) Frequency – the number of cycles or waves per unit time Unit – Hertz (Hz) Symbol – f Sound – pitch Light – color
The period of a wave is 0. 1 sec. How many waves are there in 1 second (What is the frequency)?
What is the period of a wave if 20 crests pass an observer in 4 seconds? Memorize: f = waves/time OR T = time/waves
6) Speed – how fast a wave travels v=fl A wave’s speed depends on its type and the medium it is travelling through. Sound – 346 m/s at 25 o C Light – 3 x 108 m/s in air
The frequency of a sound wave is 256 Hz. What is its wavelength? f = 256 Hz v = 346 m/s l = 1. 35 m
The frequency of a sound wave is 256 Hz. How long after it leaves a source does it take this sound wave to return from a wall that is 100 m away?
What type of wave is this?
What is the amplitude of this wave?
What is the wavelength of this wave?
If the frequency of this wave is 2. 0 Hertz, what is its period?
10 m Determine the speed of the wave.
What is the period of a wave if 15 crests pass an observer in 3 seconds? Memorize: f = waves/time OR T = time/waves
Electromagnetic Waves - all travel at the same speed (the speed of light) - all are emitted by the sun
Increasing wavelengt h Cosmic Gamma X-Rays Ultraviolet Visible Infrared Radio Decreasin g frequency
An electromagnetic wave has a -7 wavelength of 5. 37 x 10 m. What color is it?
An electromagnetic wave has a -7 wavelength of 5. 37 x 10 m. What is its period?
A sound wave has a frequency of 1. 2 MHz. a) What is its period? b) What is its wavelength?
Wave practice Problems 1. Sound waves have a frequency of 250 Hertz (waves per second) and a wavelength of 1. 30 meters. Find the speed of these sound waves. v = 325 m/s
2. Water waves in a small tank are 6 cm long. They pass a given point at a rate of 14. 8 waves every three seconds. a) What is the frequency of the water waves? b) What is the period of these water waves? c) What is the speed of these water waves? a) f = 4. 9 Hz b) T =. 2 s c) v =. 294 m/s
3. Microwaves are electromagnetic waves that travel at a speed of 3. 0 x 108 m/s. A microwave oven operates at a frequency of 2450 MHz (2. 45 x 109 waves per second) a) What is the period of these waves? T = 4. 08 x 10 -10 s b) What is the wavelength of these microwaves? l = 0. 122 m
3. Microwaves are electromagnetic waves that travel at a speed of 3. 0 x 108 m/s. A microwave oven operates at a frequency of 2450 MHz (2. 45 x 109 waves per second) c) How many microwaves fit in the oven if the length of the oven is 45 cm? 3. 7 microwaves
4. A sound pulse is directed toward the wall of a tall building that is 680 m from the source of the sound. The reflected wave is detected 4. 0 seconds after the pulse is produced. What is the speed of the sound pulse? v = 340 m/s
5. A typical light wave has a wavelength of 580 nanometers (580 x 10 -9 m). What is the frequency of this typical light wave? f = 5. 17 x 1014 Hz
6. Radio waves travel at the speed of light. Radio station KSTX broadcasts at a frequency of 89. 1 MHz. What is the wavelength of the radio station’s radio waves? l = 3. 37 m
- Slides: 36