Waves at Boundaries - Middle School Physical Science
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A wave crosses into a medium where speed is $$ times larger. What happens to wavelength if $f$ is constant?
A wave crosses into a medium where speed is $$ times larger. What happens to wavelength if $f$ is constant?
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Wavelength becomes $2\lambda$. From $v = flambda$, if $v$ doubles and $f$ stays constant, $lambda$ doubles.
Wavelength becomes $2\lambda$. From $v = flambda$, if $v$ doubles and $f$ stays constant, $lambda$ doubles.
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Which wave behavior occurs when a wave bounces back from a boundary?
Which wave behavior occurs when a wave bounces back from a boundary?
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Reflection. Waves bounce back when they hit a barrier or interface.
Reflection. Waves bounce back when they hit a barrier or interface.
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Which wave behavior occurs when a wave enters a new material and changes speed and wavelength?
Which wave behavior occurs when a wave enters a new material and changes speed and wavelength?
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Refraction. Waves bend when entering a new medium due to speed change.
Refraction. Waves bend when entering a new medium due to speed change.
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What is the name of the boundary where two different media meet?
What is the name of the boundary where two different media meet?
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Interface (boundary between media). The surface where two different materials meet.
Interface (boundary between media). The surface where two different materials meet.
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What happens to wave frequency when a wave crosses into a different medium?
What happens to wave frequency when a wave crosses into a different medium?
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Frequency stays the same. Source determines frequency; medium doesn't change it.
Frequency stays the same. Source determines frequency; medium doesn't change it.
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State the wave speed relationship among speed, frequency, and wavelength.
State the wave speed relationship among speed, frequency, and wavelength.
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$v = f\lambda$. Wave speed equals frequency times wavelength.
$v = f\lambda$. Wave speed equals frequency times wavelength.
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If wave speed decreases at a boundary and frequency stays constant, what happens to wavelength?
If wave speed decreases at a boundary and frequency stays constant, what happens to wavelength?
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Wavelength decreases. Since $v = flambda$ and $f$ is constant, $lambda$ must decrease when $v$ decreases.
Wavelength decreases. Since $v = flambda$ and $f$ is constant, $lambda$ must decrease when $v$ decreases.
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If wave speed increases at a boundary and frequency stays constant, what happens to wavelength?
If wave speed increases at a boundary and frequency stays constant, what happens to wavelength?
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Wavelength increases. Since $v = flambda$ and $f$ is constant, $lambda$ must increase when $v$ increases.
Wavelength increases. Since $v = flambda$ and $f$ is constant, $lambda$ must increase when $v$ increases.
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Which property of a mechanical wave is most directly affected by the medium it travels through?
Which property of a mechanical wave is most directly affected by the medium it travels through?
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Wave speed. Medium properties determine how fast waves propagate.
Wave speed. Medium properties determine how fast waves propagate.
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What is transmission in wave behavior at a boundary?
What is transmission in wave behavior at a boundary?
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Wave energy passes into the new medium. Wave continues into the second medium.
Wave energy passes into the new medium. Wave continues into the second medium.
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What is absorption at a boundary, in terms of wave energy?
What is absorption at a boundary, in terms of wave energy?
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Wave energy is converted to other forms (often heat). Medium absorbs wave energy, reducing amplitude.
Wave energy is converted to other forms (often heat). Medium absorbs wave energy, reducing amplitude.
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What happens to the direction of a wave when it enters a new medium at an angle and its speed changes?
What happens to the direction of a wave when it enters a new medium at an angle and its speed changes?
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It bends (changes direction). Speed change causes refraction (bending) at angles.
It bends (changes direction). Speed change causes refraction (bending) at angles.
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If a wave enters a medium where it travels slower, does it bend toward or away from the normal?
If a wave enters a medium where it travels slower, does it bend toward or away from the normal?
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Toward the normal. Slower medium bends waves toward perpendicular.
Toward the normal. Slower medium bends waves toward perpendicular.
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If a wave enters a medium where it travels faster, does it bend toward or away from the normal?
If a wave enters a medium where it travels faster, does it bend toward or away from the normal?
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Away from the normal. Faster medium bends waves away from perpendicular.
Away from the normal. Faster medium bends waves away from perpendicular.
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What is the law of reflection for wave angles at a flat boundary?
What is the law of reflection for wave angles at a flat boundary?
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Angle of incidence equals angle of reflection. Measured from normal, both angles are equal.
Angle of incidence equals angle of reflection. Measured from normal, both angles are equal.
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A wave has $f = 5\ \text{Hz}$ and enters a medium where $v = 10\ \text{m/s}$. Find $\lambda$.
A wave has $f = 5\ \text{Hz}$ and enters a medium where $v = 10\ \text{m/s}$. Find $\lambda$.
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$\lambda = 2\ \text{m}$. Using $\lambda = \frac{v}{f} = \frac{10}{5} = 2$ meters.
$\lambda = 2\ \text{m}$. Using $\lambda = \frac{v}{f} = \frac{10}{5} = 2$ meters.
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Identify the correct statement about energy at a boundary: all reflected, all transmitted, or split?
Identify the correct statement about energy at a boundary: all reflected, all transmitted, or split?
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Energy is typically split between reflected, transmitted, and absorbed parts. Conservation of energy requires distribution among all possible paths.
Energy is typically split between reflected, transmitted, and absorbed parts. Conservation of energy requires distribution among all possible paths.
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If a wave on a rope goes from heavy rope to light rope, what happens to reflected pulse orientation?
If a wave on a rope goes from heavy rope to light rope, what happens to reflected pulse orientation?
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It reflects upright (not inverted). Less dense medium acts like free boundary, preserving orientation.
It reflects upright (not inverted). Less dense medium acts like free boundary, preserving orientation.
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If a wave on a rope goes from light rope to heavy rope, what happens to reflected pulse orientation?
If a wave on a rope goes from light rope to heavy rope, what happens to reflected pulse orientation?
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It reflects inverted. Denser medium acts like fixed boundary, inverting the reflection.
It reflects inverted. Denser medium acts like fixed boundary, inverting the reflection.
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For a pulse on a rope with a free end, what is the reflection rule for the pulse orientation?
For a pulse on a rope with a free end, what is the reflection rule for the pulse orientation?
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It reflects upright (not inverted). Free boundary can move, so pulse maintains its orientation.
It reflects upright (not inverted). Free boundary can move, so pulse maintains its orientation.
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For a pulse on a rope fixed to a wall, what is the reflection rule for the pulse orientation?
For a pulse on a rope fixed to a wall, what is the reflection rule for the pulse orientation?
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It reflects inverted (up becomes down). Fixed boundary cannot move, so pulse flips to conserve momentum.
It reflects inverted (up becomes down). Fixed boundary cannot move, so pulse flips to conserve momentum.
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In a diagram of refraction, what is the “normal” line?
In a diagram of refraction, what is the “normal” line?
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A line perpendicular to the boundary at the point of incidence. Reference line for measuring angles of incidence and refraction.
A line perpendicular to the boundary at the point of incidence. Reference line for measuring angles of incidence and refraction.
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What happens to a wave’s direction when it refracts into a medium where its speed increases?
What happens to a wave’s direction when it refracts into a medium where its speed increases?
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It bends away from the normal. Faster medium causes waves to bend farther from perpendicular.
It bends away from the normal. Faster medium causes waves to bend farther from perpendicular.
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What happens to a wave’s direction when it refracts into a medium where its speed decreases?
What happens to a wave’s direction when it refracts into a medium where its speed decreases?
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It bends toward the normal. Slower medium causes waves to bend closer to perpendicular.
It bends toward the normal. Slower medium causes waves to bend closer to perpendicular.
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If a wave enters a medium where its speed increases and $f$ stays constant, what happens to $\lambda$?
If a wave enters a medium where its speed increases and $f$ stays constant, what happens to $\lambda$?
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$\lambda$ increases. Since $v = f\lambda$ and $f$ is constant, faster $v$ means larger $\lambda$.
$\lambda$ increases. Since $v = f\lambda$ and $f$ is constant, faster $v$ means larger $\lambda$.
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