Waves & Sound review

AKS 10: Wave & Sound Review

Mechanical - MUST have a medium; can be longitudinal or transverse

Electromagnetic - do NOT need a medium; transverse only

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Mechanical vs Electromagnetic Waves

Longitudinal - ex. sound

• Molecules vibrate PARALLEL to the way the wave travels

Transverse - ex. wave on string

• Molecules vibrate PERPENDICUAL to the way the wave travels

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Transverse & Longitudinal Waves

Multiple Choice

What type of wave is this?

• Transverse

• Longitudinal

Multiple Choice

Which wave travels perpendicular in relation to a medium?

• Transverse

• Longitudinal

• Both

• Neither

Multiple Choice

Which letter represents the wavelength of a wave?

• A

• B

• C

• D

Multiple Choice

In the picture, a wave is being created by shaking a rope. How would that wave be classified?

• Mechanical and Longitudinal

• Mechanical and Transverse

• Electromagnetic and Longitudinal

• Electromagnetic and Transverse

Multiple Choice

Which number represents the amplitude of the wave in the diagram?

• 1

• 2

• 3

• 4

Changing the MEDIUM will change the speed

• The more rigid the medium, the faster the speed

• The more densely packed the molecules, the faster the speed

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How to change a wave's speed

Multiple Choice

What is a medium?

• something between a small and a large?

• the substance through which a wave can travel

• a pattern of vibration that simulates when a wave is standing still

• the distance from any point on a wave to an identical point on the next wave

Multiple Choice

Which material would sound travel fastest in?

• Air

• Water

• Steel

Multiple Choice

Why does sound travel faster in water than in air?

• The particles in water are more tightly packed together

• The particles in water are more spaced apart

Multiple Choice

If you INCREASE the amplitude of a wave, the wave speed will

• increase

• decrease

• remain constant

Multiple Choice

A speaker is playing a 200 Hz note through the hot air. How could the speed of the wave be increased?

• Play the note through water instead

• Play a note with a higher frequency

• Play a note with a longer wavelength

• Play the note through cooler air instead

Multiple Choice

A person is lying which their ear on the ground and another is standing up. A heavy object is dropped. Who hears it first and why?

• Standing friend because sound travels faster in air

• Standing friend because the wave's energy is more intense through the air

• Friend on the floor because sound travels faster through solid mediums

• Friend on the floor because gravity pulls the wave down to the ground

For sound waves:

• the pitch of the sound = frequency

• the volume/intensity of the sound = amplitude

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Sound Waves

v = wave speed
f = wave frequency
λ = wavelength

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Wave Math

f = frequency - # of waves over time (Hz)
T = period - time/# of waves (s)

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Frequency & Period

Multiple Choice

A fly flaps its wings back and forth 200 times each second. Calculate the period of a wing flap.

• 200
• 0.5
• 0.05
• 0.005

Multiple Choice

A wave has frequency of 50 Hz and a wavelength of 10 m. What is the speed of the wave?

• 0.2
• 5
• 500
• 20

Multiple Choice

A wave has a period of 4 seconds. Find its frequency.

• 4
• 0.25

Multiple Choice

A sound wave has a λ of 170m. The speed of sound travels at 343 m/s. What is the frequency?

• 0.5
• 2.01
• 513
• 58.310

Multiple Choice

A kangaroo completes 3 hops in 4 seconds.  What is the frequency of the hops?

• 0.75
• 1.33
• 7
• 12