Waves at Boundaries - Middle School Physical Science

If a wave on a rope goes from light rope to heavy rope, what happens to reflected pulse orientation?

It reflects inverted. Denser medium acts like fixed boundary, inverting the reflection.
For a pulse on a rope with a free end, what is the reflection rule for the pulse orientation?

It reflects upright (not inverted). Free boundary can move, so pulse maintains its orientation.
What is absorption at a boundary, in terms of wave energy?

Wave energy is converted to other forms (often heat). Medium absorbs wave energy, reducing amplitude.
What happens to wave frequency when a wave crosses into a different medium?

Frequency stays the same. Source determines frequency; medium doesn't change it.
What is the definition of diffraction of a wave at an edge or opening?

Wave bends and spreads when it passes an edge or through an opening. Waves spread out when encountering obstacles or gaps in their path.
If wave speed decreases at a boundary and frequency stays constant, what happens to wavelength?

Wavelength decreases. Since $v = flambda$ and $f$ is constant, $lambda$ must decrease when $v$ decreases.
Identify the correct statement about energy at a boundary: all reflected, all transmitted, or split?

Energy is typically split between reflected, transmitted, and absorbed parts. Conservation of energy requires distribution among all possible paths.
What happens to a wave's direction when it refracts into a medium where its speed increases?

It bends away from the normal. Faster medium causes waves to bend farther from perpendicular.
What is the definition of transmission of a wave at a boundary?

Wave passes through a boundary into the next medium. Energy continues forward across the boundary into the new material.
If wave speed increases at a boundary and frequency stays constant, what happens to wavelength?

Wavelength increases. Since $v = flambda$ and $f$ is constant, $lambda$ must increase when $v$ increases.
Which quantity stays the same when a wave crosses into a new medium: frequency or speed?

Frequency stays the same. Source determines frequency; medium properties only affect speed.
A wave crosses into a medium where speed is times larger. What happens to wavelength if $f$ is constant?

Wavelength becomes $2\lambda$ . From $v = flambda$ , if $v$ doubles and $f$ stays constant, $lambda$ doubles.
What is the definition of absorption of a wave by a material?

Wave energy is taken in by the material and converted to other forms. Materials transform wave energy into heat or other non-wave forms.
For a pulse on a rope fixed to a wall, what is the reflection rule for the pulse orientation?

It reflects inverted (up becomes down). Fixed boundary cannot move, so pulse flips to conserve momentum.
If a wave enters a medium where its speed decreases and $f$ stays constant, what happens to $\lambda$ ?

$\lambda$ decreases. Since $v = f\lambda$ and $f$ is constant, slower $v$ means smaller $\lambda$ .
State the wave relationship that links speed, wavelength, and frequency.

$v = f\lambda$ . Fundamental equation relating wave speed, frequency, and wavelength.
If a wave enters a medium where it travels slower, does it bend toward or away from the normal?

Toward the normal. Slower medium bends waves toward perpendicular.
State the wave speed relationship among speed, frequency, and wavelength.

$v = f\lambda$ . Wave speed equals frequency times wavelength.
What is the definition of reflection of a wave at a boundary?

Wave bounces off a boundary and returns into the original medium. Energy reverses direction at the boundary, staying in the same medium.
If a wave enters a medium where it travels faster, does it bend toward or away from the normal?

Away from the normal. Faster medium bends waves away from perpendicular.
Which property of a mechanical wave is most directly affected by the medium it travels through?

Wave speed. Medium properties determine how fast waves propagate.
What happens to the direction of a wave when it enters a new medium at an angle and its speed changes?

It bends (changes direction). Speed change causes refraction (bending) at angles.
If a wave on a rope goes from heavy rope to light rope, what happens to reflected pulse orientation?

It reflects upright (not inverted). Less dense medium acts like free boundary, preserving orientation.
What is the definition of refraction of a wave at a boundary?

Wave changes speed and direction when entering a new medium. Different medium densities cause waves to bend due to speed changes.
What is the name of the boundary where two different media meet?

Interface (boundary between media). The surface where two different materials meet.
What happens to a wave's direction when it refracts into a medium where its speed decreases?

It bends toward the normal. Slower medium causes waves to bend closer to perpendicular.
Which wave behavior occurs when a wave enters a new material and changes speed and wavelength?

Refraction. Waves bend when entering a new medium due to speed change.
If a wave enters a medium where its speed increases and $f$ stays constant, what happens to $\lambda$ ?

$\lambda$ increases. Since $v = f\lambda$ and $f$ is constant, faster $v$ means larger $\lambda$ .
Which wave behavior occurs when a wave bounces back from a boundary?

Reflection. Waves bounce back when they hit a barrier or interface.
What is the law of reflection for wave angles at a flat boundary?

Angle of incidence equals angle of reflection. Measured from normal, both angles are equal.
In a diagram of refraction, what is the "normal" line?

A line perpendicular to the boundary at the point of incidence. Reference line for measuring angles of incidence and refraction.
A wave has $f = 5\ \text{Hz}$ and enters a medium where $v = 10\ \text{m/s}$ . Find $\lambda$ .

$\lambda = 2\ \text{m}$ . Using $\lambda = \frac{v}{f} = \frac{10}{5} = 2$ meters.
What is transmission in wave behavior at a boundary?

Wave energy passes into the new medium. Wave continues into the second medium.

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