Unit 3 Lesson 1 Waves Florida Benchmarks SC.7.P.10.3 Recognize that light waves, sound waves, and other waves move at different speeds in different materials. Copyright Houghton Mifflin Harcourt Publishing Company
Waves & Sound I. Characteristics of Waves Waves Transverse waves Longitudinal waves Measuring waves
A. Waves Waves Repeating disturbances that transfer energy through matter or space Medium material through which a wave transfers energy solid, liquid, gas, or combination Electromagnetic waves don t need a medium (e.g. visible light)
What are mechanical waves? Mechanical waves are waves which require a medium. A medium is a form of matter through which the wave travels (such as water, air, glass, etc.) Waves such as light, x-rays, and other forms of radiation do not require a medium.
A. Waves Two Types: Longitudinal Transverse
C. Longitudinal Waves Longitudinal Waves (a.k.a. compressional) medium moves in the same direction as wave motion In a longitudinal wave the matter in the wave moves back and forth parallel to the direction of the wave
Compressional Longitudinal wave On a compressional wave the area squeezed together is called the compression. The areas spread out are called the rarefaction. The wavelength is the distance from the center of one compression to the center of the next compression.
C. Longitudinal Waves Wave Anatomy compression rarefaction wavelength Amount of compression corresponds to amount of energy AMPLITUDE.
B. Transverse Waves Transverse Waves medium moves perpendicular to the direction of wave motion the matter in the wave moves up and down at a right angle to the direction of the wave
B. Transverse Waves Wave Anatomy wavelength crests corresponds to the amount of energy carried by the wave amplitude nodes amplitude troughs
What are the parts of a wave? Transverse wave The crest is the highest point on a transverse wave. The trough is the lowest point on a transverse wave. The wavelength is the distance from one point on the wave to the next corresponding adjacent point.
The amplitude of a transverse wave is determined by the height of the crest or depth of the trough
What is wavelength? Wavelength is a measure of distance, so the units for wavelength are always distance units, such as meter, centimeters, millimeters, etc. What is wave frequency? Frequency is the number of waves that pass through a point in one second. The unit for frequency is waves per second or Hertz (Hz). One Hz = One wave per second. Wavelength and frequency are inversely related. The smaller the wavelength, the more times it will pass through a point in one second. The larger the wavelength, the fewer times it will pass through a point in one second.
Frequency is the number of waves (vibrations) that pass through a point in one second. Period is the time it takes for one full wavelength to pass a certain point. Frequency is waves per second. Period is seconds per wave.
D. Measuring Waves Frequency ( f ) # of waves passing a point in 1 second Hertz (Hz) shorter wavelength higher frequency higher energy 1 second
A wave moving through a medium travels at a certain speed. This is Wave Speed. Wave speed is usually measured in meters/second, but may be measured using other distance units (such as centimeters per second). How is Wave Speed calculated? Wave speed is calculated as the product of a waves frequency and wavelength. Wavelength is represented by the Greek letter lambda (λ) and frequency is represented by (f)
D. Measuring Waves Velocity ( v ) speed of a wave as it moves forward depends on wave type and medium v = λ f v: velocity (m/s) λ: wavelength (m) f: frequency (Hz)
D. Measuring Waves EX: Find the velocity of a wave in a wave pool if its wavelength is 3.2 m and its frequency is 0.60 Hz. GIVEN: v =? λ = 3.2 m f = 0.60 Hz v WORK: v = λ f v = (3.2 m)(0.60 Hz) v = 1.92 m/s λ f
D. Measuring Waves EX: An earthquake produces a wave that has a wavelength of 417 m and travels at 5000 m/s. What is its frequency? GIVEN: λ = 417 m v = 5000 m/s f =? v WORK: f = v λ f = (5000 m/s) (417 m) f = 12 Hz λ f