Ch 25 Chapter Review Q & A s

Transcription

1 Ch 25 Chapter Review Q & A s a. a wiggle in time is called? b. a wiggle in space & time is called? a. vibration b. wave What is the period of a pendulum? The period is the time for 1 cycle (back & forth) How is a sine curve related to a wave? A sine curve is a pictoral representation of a wave. Distinguish between the period & the prequency of a vibration or a wave. How do they relate to one another? 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. Does the medium in which a wave travel move along with the wave itself? No, the disturbance/ energy moves not the medium. How does the speed of a wave relate to its wavelength & frequency? The velocity of the wave is equal to the product of the wavelength & frequency. As the frequency of sound is increased, does the wavelength increase or decrease? As the frequency increases, the wavelength decreases.

2 Give 2 examples of a transverse wave. water wave, wave on a string, electromagnetic wave: radio waves, microwaves infrared waves, visible light waves, ultraviolet waves, x-rays, gamma rays. Give 2 examples of a longitudinal (compression) wave. A sound wave & a seismic wave are examples of a longitudinal wave. Distinguish between a transverse wave & a longitudinal wave. Transverse: The medium moves perpendicular to wave direction Longitudinal: The medium moves back & forth parallel to wave direction Distinguish between constructive interference & destructive interference. Constructive- causes an additive effect, waves are in-phase Destructive- causes a canceling effect, waves are out-of-phase Constructive interference of sound waves results in. Increase in amplitude of wave, increased loudness, increase in decibels (db) Destructive interference of radio waves results in. Decrease in amplitude of wave, decrease in strength of signal, static sound Is interference a property of only some types of waves or of all types of waves? Interference occurs with all types of waves. What causes a standing wave? A standing wave is caused by interference of the original wave with a reflective wave

3 When a wave source moves toward a receiver, does the receiver encounter an increase in wave frequency, wave speed, or both? When a wave source moves toward a receiver, the frequency increases Does the Doppler effect occur for only some types of waves or all types of waves? The Doppler effect occurs with all waves. Explain the Doppler effect on sound waves? As the sound source moves towards receiver, the frequency & pitch increase As the sound source moves away from receiver, the frequency & pitch decreases Explain the Doppler effect on light waves? 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 Explain the Doppler effect on radar waves? Radar wave reflects off of a car moving toward police radar gun, frequency increases, How fast must a bug swim to keep up with the wave it is producing? As fast as the waves move How fast must a boat move to produce a bow wave? A boat must move faster than the bow wave moves.

4 Distinguish between a bow wave and a shock wave. Bow- a 2-D V on the water surface Shock- a 3-D cone in the air What is a sonic boom? continuous front of high pressure made by faster-than-sound sources 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 No, it could have occurred any time ago. Sonic boom depends on speed, not time Red light has a longer wavelength than violet light. Which has the greater frequency? The speed/velocity of all visible light is the same, so the wave with the shorter wavelength has the greater frequency- violet If you triple the frequency of a vibrating object, what will happen to its period? f & T are reciprocals of each other, so tripling the frequency results in 1/3 the period How far, in terms of wavelength, does a wave travel in one period? 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 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? the wave travels at the same speed in all directions.

5 Why is it that a subsonic aircraft, no matter how loud it may be, cannot produce a sonic boom? 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. A nurse counts 76 heartbeats in one minute. What are the period & frequency of of the heart oscillations? T = 1/76 minutes f = 76 beats/ minute (bpm) A skyscraper oscillates in the wind with a period of 6.8 s. Calculate its frequency & wavelength v = wavelength x f = (0.15 m)(2 Hz) = (0.15m) (2 1/s) = 0.3 m / s Calculate the velocity of waves in water that are 0.4 m apart and have a frequency of 2 Hz. v = (wavelength) ( frequency) = (0.4m) (2 1/ s) = (0.4m ) ( 2 Hz) = 0.8 m/ s 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. wavelength = velocity / frequency = (340 m/ s) (20 Hz) = 17 m

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