Ch 25 Chapter Review Q & A’s
Q: a. a wiggle in time is called ___? b. a wiggle in space & time is called?
A: a. vibration b. wave
Q: What is the period of a pendulum?
A: The period is the time for 1 cycle (back & forth)
Q: How is a sine curve related to a wave?
A: A sine curve is a pictoral representation of a wave.
Q: Distinguish between the period & the prequency of a vibration or a wave. How do they relate to one another?
A: The period is the time to complete one cycle. Frequency is how many cycles occur in a given time. Period & Frequency are reciprocals of each other; inversely related.
Q: Does the medium in which a wave travel move along with the wave itself?
A: No, the disturbance/ energy moves not the medium.
Q: How does the speed of a wave relate to its wavelength & frequency?
A: The velocity of the wave is equal to the product of the wavelength & frequency.
Q: As the frequency of sound is increased, does the wavelength increase or decrease?
A: As the frequency increases, the wavelength decreases.
Q: Give 2 examples of a transverse wave.
A: water wave, wave on a string, electromagnetic wave: radio waves, microwaves infrared waves, visible light waves, ultraviolet waves, x-rays, gamma rays.
Q: Give 2 examples of a longitudinal (compression) wave.
A: A sound wave & a seismic wave are examples of a longitudinal wave.
Q: Distinguish between a transverse wave & a longitudinal wave.
A: Transverse: The medium moves perpendicular to wave direction
Longitudinal: The medium moves back & forth parallel to wave direction
Q: Distinguish between constructive interference & destructive interference.
A: Constructive- causes an additive effect, waves are in-phase Destructive- causes a canceling effect, waves are out-of-phase
Q: Constructive interference of sound waves results in___.
A: Increase in amplitude of wave, increased loudness, increase in decibels (db)
Q: Destructive interference of radio waves results in ___.
A: Decrease in amplitude of wave, decrease in strength of signal, static sound
Q: Is interference a property of only some types of waves or of all types of waves?
A: Interference occurs with all types of waves.
Q: What causes a standing wave?
A: A standing wave is caused by interference of the original wave with a reflective wave
Q: When a wave source moves toward a receiver, does the receiver encounter an increase in wave frequency, wave speed, or both?
A: When a wave source moves toward a receiver, the frequency increases
Q: Does the Doppler effect occur for only some types of waves or all types of waves?
A: The Doppler effect occurs with all waves.
Q: Explain the Doppler effect on sound waves?
A: As the sound source moves towards receiver, the frequency & pitch increase As the sound source moves away from receiver, the frequency & pitch decreases
Q: Explain the Doppler effect on light waves?
A: As the light source moves towards receiver, frequency increases, light shifts to blue As the light source moves away from receiver, frequency decreases, light shifts to red
Q: Explain the Doppler effect on radar waves?
A: Radar wave reflects off of a car moving toward police radar gun, frequency increases,
Q: How fast must a bug swim to keep up with the wave it is producing?
A: As fast as the waves move
Q: How fast must a boat move to produce a bow wave?
A: A boat must move faster than the bow wave moves.
Q: Distinguish between a bow wave and a shock wave.
A: Bow- a 2-D “V” on the water surface Shock- a 3-D cone in the air
Q: What is a sonic boom?
A: continuous front of high pressure made by faster-than-sound sources
Q: If you encounter a sonic boom, is that evidence that an aircraft of some sort exceeded the speed of sound moments ago to become supersonic
A: No, it could have occurred any time ago. Sonic boom depends on speed, not time
Q: Red light has a longer wavelength than violet light. Which has the greater frequency?
A: The speed/velocity of all visible light is the same, so the wave with the shorter wavelength has the greater frequency- violet
Q: If you triple the frequency of a vibrating object, what will happen to its period?
A: f & T are reciprocals of each other, so tripling the frequency results in 1/3 the period
Q: How far, in terms of wavelength, does a wave travel in one period?
A: A wave takes a time equal to one period to travel a distance of one wavelength.
Distance = velocity x time = (wavelength x frequency) x period = (wavelength x 1/T ) ( T ) = wavelength
Q: The wave patterns made by tapping water create circular circles. What does this tell you about the speed/ velocity of the waves in different directions?
A: the wave travels at the same speed in all directions.
Q: Why is it that a subsonic aircraft, no matter how loud it may be, cannot produce a sonic boom?
A: At subsonic speeds, there is no overlapping of waves to produce high-pressure regions, where there is no shock wave, there is no sonic boom.
Q: A nurse counts 76 heartbeats in one minute. What are the period & frequency of of the heart oscillations?
A: T = 1/76 minutes f = 76 beats/ minute (bpm)
Q: A skyscraper oscillates in the wind with a period of 6.8 s. Calculate its frequency &
wavelength
A: v = wavelength x f = (0.15 m)(2 Hz) = (0.15m) (2 1/s) = 0.3 m / s
Q: Calculate the velocity of waves in water that are 0.4 m apart and have a frequency of 2 Hz.
A: v = (wavelength) ( frequency) = (0.4m) (2 1/ s) = (0.4m ) ( 2 Hz) = 0.8 m/ s
Q: The lowest frequency we can hear is about 20 Hz. Calculate the wavelength associated with this frequency for sound that travels at 340 m/ s.
A: wavelength = velocity / frequency = (340 m/ s) (20 Hz) = 17 m
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