General Principles and Properties - MCAT Physical
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Which of these is an example of a longitudinal wave?
Which of these is an example of a longitudinal wave?
Longitudinal waves transmit energy by compressing and rarefacting the medium in the same direction as they are traveling. Sounds waves are longitudinal waves and travel by compressing the air through which they travel, causing vibration.
Light, X-rays, and microwaves are all examples of electromagnetic waves; even if you cannot recall if they are longitudinal or transverse, they are all members of the same phenomenon and will have the same type of wave transmission. Transverse waves are generated by oscillation within a plane perpendicular to the direction of motion. Oscillating a rope is a transverse wave, as it is not compressing in the direction of motion.
Longitudinal waves transmit energy by compressing and rarefacting the medium in the same direction as they are traveling. Sounds waves are longitudinal waves and travel by compressing the air through which they travel, causing vibration.
Light, X-rays, and microwaves are all examples of electromagnetic waves; even if you cannot recall if they are longitudinal or transverse, they are all members of the same phenomenon and will have the same type of wave transmission. Transverse waves are generated by oscillation within a plane perpendicular to the direction of motion. Oscillating a rope is a transverse wave, as it is not compressing in the direction of motion.
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At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of 
, where T is the temperature in °C.
What type of waves are sound waves?
At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of
What type of waves are sound waves?
Sound waves are longitudinal waves, meaning that the waves propagate by compression and rarefaction of their medium. They are termed longitudinal waves because the particles in the medium through which the wave travels (air molecules in our case) oscillate parallel to the direction of motion. Alternatively, transverse waves oscillate perpendicular to the direction of motion. Common examples of transverse waves include light and, to a basic approximation, waves on the ocean.
Sound waves are longitudinal waves, meaning that the waves propagate by compression and rarefaction of their medium. They are termed longitudinal waves because the particles in the medium through which the wave travels (air molecules in our case) oscillate parallel to the direction of motion. Alternatively, transverse waves oscillate perpendicular to the direction of motion. Common examples of transverse waves include light and, to a basic approximation, waves on the ocean.
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All of the following are transverse waves, except __________.
All of the following are transverse waves, except __________.
An important distinction for the MCAT is the difference between transverse and longitudinal waves. Although both wave types are sinusoidal, transverse waves oscillate perpendicular to the direction of propagation, while longitudinal waves oscillate parallel to the direction of propagation.
The most common transverse and longitudinal waves are light waves and sound waves, respectively. All electromagnetic waves (light waves, microwaves, X-rays, radio waves) are transverse. All sound waves are longitudinal.
An important distinction for the MCAT is the difference between transverse and longitudinal waves. Although both wave types are sinusoidal, transverse waves oscillate perpendicular to the direction of propagation, while longitudinal waves oscillate parallel to the direction of propagation.
The most common transverse and longitudinal waves are light waves and sound waves, respectively. All electromagnetic waves (light waves, microwaves, X-rays, radio waves) are transverse. All sound waves are longitudinal.
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Which of the following is a standing wave?
Which of the following is a standing wave?
A simple definition of a standing wave is a wave that is self-reinforcing, which is to say that reflection of the wave through the medium results in some areas of amplification (anti-nodes) of the wave and some areas of nullification (nodes). In other words, resonance must occur, and that usually suggests confinement of the wave in some fashion.
A fan and a bus make noise and vibration, but the sound does not resonate. It is transmitted, but not confined. Light with a specific wavelength has no "resonant" character, and neither do waves striking a pier. If the waves were confined in a harbor so that they could amplify, it might be possible to produce a standing wave. Microwaves trapped inside a microwave oven have this feature, producing antinodes of intense heating and nodes where no energy is transmitted into the food; this is the reason that microwave ovens have rotating platforms to make heating of the food item more uniform.
A violin string will be seen to have discrete, stable regions of motion and lack of motion, the requirements of the standing wave phenomenon. The points of reflection on the string are the two ends. The vibration of the wave is confined within the string, amplifying the sound as the nodes overlap.
A simple definition of a standing wave is a wave that is self-reinforcing, which is to say that reflection of the wave through the medium results in some areas of amplification (anti-nodes) of the wave and some areas of nullification (nodes). In other words, resonance must occur, and that usually suggests confinement of the wave in some fashion.
A fan and a bus make noise and vibration, but the sound does not resonate. It is transmitted, but not confined. Light with a specific wavelength has no "resonant" character, and neither do waves striking a pier. If the waves were confined in a harbor so that they could amplify, it might be possible to produce a standing wave. Microwaves trapped inside a microwave oven have this feature, producing antinodes of intense heating and nodes where no energy is transmitted into the food; this is the reason that microwave ovens have rotating platforms to make heating of the food item more uniform.
A violin string will be seen to have discrete, stable regions of motion and lack of motion, the requirements of the standing wave phenomenon. The points of reflection on the string are the two ends. The vibration of the wave is confined within the string, amplifying the sound as the nodes overlap.
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What phenomenon can occur with light, but not sound?
What phenomenon can occur with light, but not sound?
Sound is a longitudinal wave, while light is a transverse wave. Polarization requires the direction of the wave to be perpendicular to the direction of propogation; only light can do this. Doppler effect, refraction, and interference occur in both wave types.
Sound is a longitudinal wave, while light is a transverse wave. Polarization requires the direction of the wave to be perpendicular to the direction of propogation; only light can do this. Doppler effect, refraction, and interference occur in both wave types.
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Which statement is not true for all waves?
Which statement is not true for all waves?
The speed of sound is dependent on the temperature of the transmitting medium. The speed of light is not.
The speed of sound is dependent on the temperature of the transmitting medium. The speed of light is not.
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Sound traveling at a velocity, V1, through a certain medium will travel at what velocity through a medium of twice the density?
Sound traveling at a velocity, V1, through a certain medium will travel at what velocity through a medium of twice the density?
The speed of sound depends on both the medium’s density and resistance to compression. We do not have enough information to solve for V2 in terms of V1.
The speed of sound depends on both the medium’s density and resistance to compression. We do not have enough information to solve for V2 in terms of V1.
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A wave produced on a string travels with a velocity of 
. If the tension on the string is increased by a factor of four, at what speed does the wave travel?
A wave produced on a string travels with a velocity of
The velocity of a wave can be obtained with the formula 
, where 
is the tension in the string and 
is the mass per unit length of the string. Since the tension is quadrupled, the velocity will be doubled.
Let's assume that a string with tension 
and a mass per unit length 
produces a wave with velocity 
.
If we increase the tension by a factor of four, we will get the below expression.
We can see that 
, and we know that 
.
The velocity of a wave can be obtained with the formula
Let's assume that a string with tension
If we increase the tension by a factor of four, we will get the below expression.
We can see that
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At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of 
, where T is the temperature in °C.
How does the speed of sound in the summer (30oC) compare to the speed of sound in the winter (9oC)?
At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of
How does the speed of sound in the summer (30oC) compare to the speed of sound in the winter (9oC)?
This question asks us to use information provided in the paragraph about how the speed of sound varies with temperature. We can see from the relationship provided that in warmer temperatures the speed of sound is faster. This intuitively makes sense—hotter temperatures mean that air molecules are moving around more, and thus have less resistance to compression or rarefaction by a propagating sound wave. Now that we have a qualitative understanding, we need to compute the ratio of the velocities.
This question asks us to use information provided in the paragraph about how the speed of sound varies with temperature. We can see from the relationship provided that in warmer temperatures the speed of sound is faster. This intuitively makes sense—hotter temperatures mean that air molecules are moving around more, and thus have less resistance to compression or rarefaction by a propagating sound wave. Now that we have a qualitative understanding, we need to compute the ratio of the velocities.
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At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of 
, where T is the temperature in °C.
How long would it take for a 30Hz beat to reach an audience member 100m away when the ambient temperature is 21ºC?
At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of
How long would it take for a 30Hz beat to reach an audience member 100m away when the ambient temperature is 21ºC?
The question asks us to determine how long it will take for a wave beat to reach an audience member at 100m away; thus, we need to calculate the velocity of the wave to determine the time.
We know from kinematics that 
. This can be rearranged to solve for t: 
.
The question asks us to determine how long it will take for a wave beat to reach an audience member at 100m away; thus, we need to calculate the velocity of the wave to determine the time.
We know from kinematics that
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Through which of the following would you expect a photon to travel fastest?
Through which of the following would you expect a photon to travel fastest?
A photon will travel fastest through a vacuum. Photons are generally massless and can be thought of as a light wave, which travels fastest in a vacuum and slowest through a metal or solid. This can be visualized using the concept of the index of refraction, which describes the speed of light through air compared to the speed through other mediums. A vacuum will be the least dense and cause the least hindrance to a photon as it travels, thus giving it the lowest index of refraction and allowing the fastest speed of light.
A photon will travel fastest through a vacuum. Photons are generally massless and can be thought of as a light wave, which travels fastest in a vacuum and slowest through a metal or solid. This can be visualized using the concept of the index of refraction, which describes the speed of light through air compared to the speed through other mediums. A vacuum will be the least dense and cause the least hindrance to a photon as it travels, thus giving it the lowest index of refraction and allowing the fastest speed of light.
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You are out snorkling off the coast of an exotic island when a pod of whales comes swimming by. The pod is 100m away. If they emit sounds underwater with an average frequency of 2200Hz and there are 500 complete sound waves between you and the pod, how fast is the speed of sound in the water?
You are out snorkling off the coast of an exotic island when a pod of whales comes swimming by. The pod is 100m away. If they emit sounds underwater with an average frequency of 2200Hz and there are 500 complete sound waves between you and the pod, how fast is the speed of sound in the water?
If there are 500 waves over a distance of 100 meters, we can say that the wavelength is:
Now we can use the formula for the speed of waves:
If there are 500 waves over a distance of 100 meters, we can say that the wavelength is:
Now we can use the formula for the speed of waves:
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A stretched string of length L, mass M, and tension T is vibrating at its fundamental frequency. Which of the following changes takes place if the vibration frequency of the string increases, but tension and mass density remain constant?
A stretched string of length L, mass M, and tension T is vibrating at its fundamental frequency. Which of the following changes takes place if the vibration frequency of the string increases, but tension and mass density remain constant?
We can use the equation 
together with 
. If T is constant, v cannot change assuming the mass density, m/L, is constant. Thus, 
must be constant; if f increases, 
must decrease.
We can use the equation
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Picture a transverse wave traveling through water. After the crest of one wave hits a stationary object in the water, an observer counts eight more crests hitting the same object in fifteen seconds. The frequency of the waves is __________.
Picture a transverse wave traveling through water. After the crest of one wave hits a stationary object in the water, an observer counts eight more crests hitting the same object in fifteen seconds. The frequency of the waves is __________.
Right away you can rule out the answers with units in seconds, as the unit of frequency is an inverse second, or Hz. Frequency is measured in cycles per second. If eight crests pass a given point in fifteen seconds, the frequency is given by the number of crests divided by the time period.
Right away you can rule out the answers with units in seconds, as the unit of frequency is an inverse second, or Hz. Frequency is measured in cycles per second. If eight crests pass a given point in fifteen seconds, the frequency is given by the number of crests divided by the time period.
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A transverse wave has a velocity of 5.2m/s. If ten cycles pass a given point in 1.6s, what are the wave’s period and wavelength?
A transverse wave has a velocity of 5.2m/s. If ten cycles pass a given point in 1.6s, what are the wave’s period and wavelength?
First calculate the frequency of the wave (cycles/sec). The problem tells us that there are ten cycles in 1.6s.
Next find the period by taking the inverse of the frequency.
Finally, find the wavelength by dividing the velocity by the frequency.
First calculate the frequency of the wave (cycles/sec). The problem tells us that there are ten cycles in 1.6s.
Next find the period by taking the inverse of the frequency.
Finally, find the wavelength by dividing the velocity by the frequency.
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What are the frequency and wavelength of a sound wave with a period of 0.04s and a velocity of 575m/s?
What are the frequency and wavelength of a sound wave with a period of 0.04s and a velocity of 575m/s?
Solve for frequency by taking the inverse of the period.
Next, solve for wavelength by dividing velocity by frequency.
Solve for frequency by taking the inverse of the period.
Next, solve for wavelength by dividing velocity by frequency.
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What is the beat frequency if f1 = 200Hz and f2 = 150Hz?
What is the beat frequency if f1 = 200Hz and f2 = 150Hz?
Beat frequency is the difference between the two frequencies.
200Hz – 150Hz = 50Hz
Beat frequency is the difference between the two frequencies.
200Hz – 150Hz = 50Hz
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What is the frequency of a typical soundwave traveling at 340m/s with a wavelength of 40mm?
What is the frequency of a typical soundwave traveling at 340m/s with a wavelength of 40mm?
Using the equation 
we can find the frequency of the soundwave.
Using the equation
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What is the wavelength of a sound traveling at a frequency of 3000Hz?
What is the wavelength of a sound traveling at a frequency of 3000Hz?
The wavelength of a sound can be found by utilizing the equation, 
. where v is the velocity of sound, 
is the wavelength, and f is the frequency. You should know that sound normally travels with a speed of 340m/s, unless otherwise stated. With the information given we can find the wavelength of the traveling sound to be 0.11m.
The wavelength of a sound can be found by utilizing the equation,
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An incandescent light bulb is shown through a glass prism. The certain wavlength of the light is then directed into a glass cuvette containing an unknown concentration of protein. Commonly, this process is called spectroscopy and is used to determine the concentrations of DNA, RNA, and proteins in solutions. The indices of reflection of air, glass, and the solution are 1, 1.5, and 1.3, respectively.
What property of light does not change when it enters the prism?
An incandescent light bulb is shown through a glass prism. The certain wavlength of the light is then directed into a glass cuvette containing an unknown concentration of protein. Commonly, this process is called spectroscopy and is used to determine the concentrations of DNA, RNA, and proteins in solutions. The indices of reflection of air, glass, and the solution are 1, 1.5, and 1.3, respectively.
What property of light does not change when it enters the prism?
The frequency of light does not change when it enters a medium with a different index of refraction; in this case, that new medium is the glass of the prism. From the velocity of light equation we know the relationship between velocity and frequency.
v is the velocity of light, 
is the wavelength, and f is the frequency. When light enters the prism, its velocity changes due to the new index of refraction, but its frequency remains constant.
Because the frequency does not change, we can see that velocity is directly proportional to wavelength; thus, the shorter the wavelength, the slower the velocity. So both wavelength and velocity change when frequency is constant.
The frequency of light does not change when it enters a medium with a different index of refraction; in this case, that new medium is the glass of the prism. From the velocity of light equation we know the relationship between velocity and frequency.
v is the velocity of light,
Because the frequency does not change, we can see that velocity is directly proportional to wavelength; thus, the shorter the wavelength, the slower the velocity. So both wavelength and velocity change when frequency is constant.
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