Energy in Waves

Waves Intro pt 2: Waves and Energy Relations​

by Ms. Taylor​

​Waves Intro Review

• ​Waves are disturbances carrying energy.

• ​Transverse waves have vibrations moving perpendicular to the energy flow.

• ​Longitudinal waves have energy and vibrations in same direction

Multiple Choice

What kind of wave is this?

• electromagnetic

• longitudinal

• transverse

Multiple Choice

#1 refers to the

• wavelength

• amplitude

• crest

• trough

Multiple Choice

#2 refers to the

• wavelength

• amplitude

• crest

• trough

Multiple Choice

#3 refers to the

• wavelength

• amplitude

• crest

• trough

Multiple Choice

#4 refers to the

• wavelength

• amplitude

• crest

• trough

​Amplitude and Energy

• The amount of energy moving through a medium determines the size of the wave.

• A small amount of energy will create a smaller disturbance hence, smaller wave. A large amount of energy will create a larger disturbance and wave.

• Waves with more energy have higher amplitudes. Waves with less energy have lower amplitudes.

• ​High amplitude=high energy.

• Amplitude does NOT affect frequency, wavelength or the wave speed.

​Wave Speed

• ​Wave travels at different speed depending on the medium it is in.

• ​Mechanical waves travel fastest in solid medium as the particles are closer together to vibrate more.

• Mechanical Waves travel faster in Liquids than in gases (think of delay between lightning and thunder)

​Wavength, Frequency and Energy

• ​As wavelength increases, less waves will pass an area per second. Hence, frequency decreases.

• ​Less waves moving over an area per second means less energy being transferred.

• ​Higher frequencies means waves are passing quicker so more energy.

• More waves passing in a second means the distance between them is shorter, hence, shorter wavelength.

• ​​Shorter Wavelength = higher the frequency = greater energy.

• Longer wavelengths = lower the frequency = lower energy.

Multiple Choice

As wavelength decreases, the crests of the wave:

• become wider

• become shorter

• get closer together

• get farther apart

Multiple Choice

What medium do sound waves travel fastest through?

• Solids

• Liquids

• Gases

Multiple Choice

If a sound waves moves from a gas to a liquid, the sound wave will

• speed up

• slow down

• not change speed

Multiple Choice

A wave with a large wavelength will have a ______ frequency and _____ energy

• high, low

• high, high

• low, high

• low, low

Multiple Choice

High frequency waves have _________ wavelength.

• varying
• high
• the same
• low

​Wavelength, Wave speed and Frequency Relationship

• ​Frequency is INVERSELY proportional to Wavelength.

• Therefore, doubling one means halving the other.

• ​​This will NOT affect the wave speed. That is, doubling frequency or wavelength will produce the SAME wave speed.

• ​

• ​Wave speed= Frequency x Wavelength

​The only way to change the wave speed is to change the medium.

Multiple Choice

A wave has a speed of 150 m/s and a wavelength of 10 m. What is its frequency?

• 15 Hz

• 50 Hz

• 10 Hz

Multiple Choice

If 6 waves pass a point every 2 seconds, what is the frequency?

• 6 Hz

• 3 Hz

• 12 Hz

Multiple Choice

A wave with a frequency of 14 Hz has a wavelength of 3 m. What is its speed?

• 65 m/s

• 42 m/s

• 4.7 m/s