waves and sound Flashcards
it is a raveling disturbance that carries energy from one place to another.
wave
Does a wave move objects from place to place?
No, waves carry energy, not objects.
A wave where the disturbance moves parallel to the wave’s direction.
longitudinal wave
- a sound wave is a longitudinal wave
- particles move back and forth in the same direction as the waves traves
A wave where the disturbance moves perpendicular to the wave’s direction.
transverse wave
- examples: light waves, radio waves, microwave and waves on guitar string
- particles move up and down, perpendicular to the direction the wave travels
Waves that repeat cycles or patterns over and over, like rhythmic slinky waves.
periodic waves
- formed when the source moves in simple harmonic motion
- back and forth repetitive movement where displacement on both sides of a central position
- example: swinging pendulum or a vibrating slinky.
what happens to each part of a slinky in a periodic wave?
Each segment vibrates in simple harmonic motion.
A wave that looks like it’s not moving, formed when two waves traveling in opposite directions combine.
standing wave
- formed by the superposition of two waves with the same frequency, amplitude, and direction.
A point on a standing wave with maximum oscillation.
antinode
A point on a standing wave with zero oscillation that appears fixed.
node
How can you create a standing wave?
Use a traveling wave and its reflection to ensure they combine with the same frequency and amplitude.
A is the maximum excursion of a particle of the medium from the particles undisturbed position.
amplitude
it is the horizontal length of one cycle of the wave.
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wavelength
it is the time required for one complete cycle.
period
it is related to the period and has units of Hz, or s-1
frequency
What is the relationship between speed, wavelength, and frequency?
Speed = Wavelength × Frequency
What determines the speed of a wave on a string?
How quickly a particle of the string is accelerated upward by the pulling force.
What causes upward acceleration in a string wave?
The net pulling force acting on the string.
A longitudinal wave created by vibrating objects, moving through a medium.
sound
Can sound travel in a vacuum?
No, sound needs a medium like air, liquid, or solid to travel.
condensations vs rarefactions
condensations:
areas where particles are close together
rarefactions:
are where particles are spread apart in a sound wave.
hat happens to air molecules in a sound wave?
They vibrate back and forth but do not travel with the wave.
What is the wavelength of a sound wave?
The distance between two adjacent condensations or rarefactions.
it is the number of cycles per second.
frequency
A sound with a single frequency
pure tone
The brain interprets the frequency in terms of the subjective quality
pitch
it is an attribute of a sound that depends primarily on the pressure amplitude of the wave
loudness
true or false:
Sound travels through gases, liquids, and solids at considerably different speeds.
true
the power passing through a surface divided by the area of that surface.
sound intensity
How does sound intensity change with the area?
The smaller the area, the higher the intensity; the larger the area, the lower the intensity.
What happens to the intensity of sound if the energy is spread over a large area?
The intensity is lower (the sound is quieter).
The amount of energy transported by the sound wave per second.
power of a wave sound
What is the threshold of hearing?
The smallest sound intensity that the human ear can detect, about
1×10 ^−12 W/m² for a 1000 Hz tone.
At what intensity can sound become painful to hear?
Continuous exposure to intensities greater than 1 W/m² can be painful.
How does distance from the sound source affect intensity?
The intensity decreases as you move farther from the source.
How is sound emitted from a source in terms of intensity?
sound is emitted uniformly in all directions, so the intensity depends on the distance from the source.
What is the unit used to measure sound intensity?
the decibel (dB) is used to measure and compare sound intensities
What is the formula for intensity level in decibels?
index card
What happens when the intensity of a sound equals 𝐼0?
The intensity level is zero because
log(1)=0
Why is the decibel scale logarithmic?
The human ear responds to sound intensity in a way that is better represented on a logarithmic scale.
the change in frequency or pitch of sound due to the motion of the sound source or observer.
Doppler Effect
What happens to the pitch of an ambulance siren as it moves toward you?
The pitch gets higher as it approaches and lower as it moves away.
How does ultrasound help in medicine?
Ultrasound uses sound waves to create images and also to treat tumors by vibrating at high frequencies.
It measures changes in sound frequency as the sound bounces off moving objects like red blood cells, helping doctors track blood flow.
Doppler ultrasound
How does sound help break apart tumors in medicine?
Ultrasonic waves vibrate at 23 kHz, which can shatter parts of a tumor when directed at it.
