Waves And Oscillation Flashcards
Define waves (3)
-an oscillation that propagates from one place to another
-they oscillate at well defined speeds determined by the property of the material
-they carry energy
State 2 types of waves (2)
-Longitudinal
-transverse
Define transverse waves (2)
-a wave in which particles oscillate perpendicular to the direction of the wave travel
-they show crest and troughs
State examples of transverse waves (2)
-light
-electromagnetic waves
Define longitudinal waves (2)
-a wave in which particles oscillate parallel to the direction of wave and energy transfer
-they show areas of compression and rarefaction
What does compression mean (1)
-areas of increased pressure and density
What does rarefaction mean (1)
-areas of decreased pressure
State examples of longitudinal waves (2)
-sound waves
-ultrasound waves
Why are longitudinal and transverse waves also called as harmonic waves (2)
-because they’re waves where the pattern of disturbance repeats regularly
What are the key features of harmonic waves (3)
-equal spacing
-regular pattern
-well defined frequency
How is energy transmitted through longitudinal waves (3)
-particles in the medium vibrate as they are given energy
-the compression causes the nearby particles to also vibrate with more energy
-this produces a compression further along the medium
Define wavelength (2)
-distance over which a wave repeats
-length of one whole cycle
Define frequency (1)
-number of vibration per unit time passing a given point
Define period (1)
-the time taken for a whole cycle to complete
Define amplitude (1)
-maximum displacement of a wave from its stationary point
State the formula of frequency (2)
F = 1/ period
F = speed of wave / wavelength
State the formula for speed of wave (1)
Speed of wave = distance / time
What is the speed of sound in air under normal ATM and temperature (1)
V = 343m/s
How is speed determined in solids (1)
-the stiffer the material, the faster the sound wave is
(Sometimes to calculate speed of sound you may have to use Kinematics equations)
You drop a stone from rest into a well that is 7.35m deep. How long does it take before you hear a splash (3)
Distance = UT + 1/2at^2
7.35 = 0xt + 1/2x9.81xt2
T= 1.22
Distance = velocity x time
7.35/343
T = 0.0214s
T = T1 + T2
0.0214 + 1.22
=1.24s
How is the pitch of sound determined (1)
By frequency
What is the range of pitch humans can hear (1)
20Hz - 20,000Hz
Define ultrasonic (1)
Sounds with the frequencies above the human hearing range
Define infrasonic (1)
Sounds with frequencies below the human hearing range
What are the medical application of ultrasonic (1)
-used to image a fetus in the womb by sending burst of ultrasound into the body and measuring the time delay of echos
How is the loudness of sound determined and define it (2)
-By Intensity
-which is by the amount of energy that passes through a given area in a given time
State the formula for intensity of sound (2)
Intensity = energy/ (area x time)
Intensity = power/area
Why does the intensity of sound decreases as we move away from the sound
And state a formula for intensity with respect to distance (2)
-energy emerged per time by the source spreads out over a large area
Intensity with distance = power/ (4 x pie x distance^2)
SI unit = w/m^2
OR
Intensity2 = (distance1 / distance2)^2 x intensity1. [this formula is used when have to find another intensity]
How is the speed of a wave determined (1)
-by the properties of the medium through which it propagates
Speed = distance/time
What are the characteristics that determine the speed of a wave (2)
-tension in the string
-mass of the string
Why is tension required to form a wave ? (2)
-it provides the restoring force necessary to establish and sustain a wave motion
-if the tension is increases the string becomes less slack so waves will travel though the string more rapidly
How does mass affect the motion of wave (2)
-the heavier a rope or string, the slower the speed of wave on it
-because a heavy string responds slowly to a given disturbance due to its inertia
State the equation of mass per length (1)
Mass per length = mass / length
State the equation of speed of wave on a string (1)
Speed = square root ( force / mass per length )
A rope of length L and mass M hangs from a ceiling. If the bottom of the rope is given a gentle wiggle, a wave will travel to the top of the rope. As the wave travels upwards does it’s speed increase, decrease or stay the same (4)
Increases
-because mass per length is same top to bottom
-tension is zero at the bottom and increases to MG ti the top
-tension increases with height so does speed
Define periodic motion (1)
A motion that repeats itself over time
