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Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Mar 27, 2015

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Dylan Henry

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Page 1: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Chapter 20

Page 2: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

What do you think of when you hear the word “wave”? Write a brief description of what you know about them.

Page 3: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. Light waves are mechanical waves because they must travel in a medium.

2. In space, no one can hear an explosion.

3. Water waves are a combination of longitudinal and transverse waves.

Page 4: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Imagine that your family has just returned home from a day at the beach. You had fun, but you are hungry from playing in the ocean under a hot sun. You put some leftover pizza in the microwave for dinner and you turn on the radio. Just then the phone rings.

In the events described above, how many different waves were present? List them.

Page 5: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

There are at least 51. Water waves in the ocean2. Microwaves in the microwave oven3. Light waves from the sun4. Radio waves transmitted TO the radio5. Sound waves from the phone and

radio6. Did you come up with any others?

Page 6: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

If you are seen, heard or otherwise detected, it is the result of waves!!!

A wave is any disturbance that transmits energy through matter or space.

Page 7: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

When you shake a rope, the rope only goes up and down…..the ENERGY is all that moves forward and backwards.

Sound moves through the air, but you don’t feel a breeze every time you hear a noise….the air doesn’t travel with the sound wave…

Page 8: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

A medium is a substance through which a wave can travel.

A medium can be a solid, liquid or gas It travels through vibrating

particles…..they pass the energy from one particle to the next…..

Page 9: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Any type of wave that requires a medium to travel through is called a mechanical wave

Sound waves, water waves and seismic waves require a medium…

No air……means no sound!!!

Page 10: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Waves that DO NOT require a medium to travel through are called electromagnetic waves.

Visible light, microwaves, radio waves (radio waves are NOT sound waves), ultraviolet light, x-rays and gamma rays are all electromagnetic waves.

Page 11: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Waves are classified based on the direction in which the particles of the wave move.

Page 12: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Transverse waves are waves in which the particles vibrate in an up and down motion.

The crest is the highest point on the wave.

The trough is the lowest point between each crest.

Page 13: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.
Page 14: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Longitudinal Waves are waves in which the particles vibrate in a back and forth motion.

The area where particles are crowded together is called a compression.

The area where particles are spread out is called a rarefaction.

Page 15: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.
Page 16: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. A wave is a disturbance that travels through ______________ or _____________.

Page 17: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. A wave is a disturbance that travels

through matter or space.

Page 18: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

2. A wave carries _____________.

Page 19: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

2. A wave carries energy.

Page 20: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

3. Waves that require a medium are called _____________ waves.

4. Waves that DO NOT require a medium are called _____________ waves.

Page 21: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

3. Waves that require a medium are

called mechanical waves.

4. Waves that DO NOT require a medium

are called electromagnetic waves.

Page 22: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. Describe how transverse waves differ from longitudinal waves.

2. Why can’t you cause a floating leaf to move to the edge of a pond by throwing stones behind it?

3. Explain why supernova explosions in space can be seen but not heard on Earth.

4. Sometimes people at sports events do “the wave”. Do you think this a real example of a wave? Why or why not?

Page 23: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

What would happen if a transverse and longitudinal wave happened at the same time?

What type of movement would the energy have?

Page 24: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

How do we measure the properties and characteristics of waves? There are 4 basic properties.

1. Amplitude2. Wavelength3. Frequency

4. Wave Speed

Page 25: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Amplitude is the maximum distance a wave travels from its resting position.

Page 26: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

If you had a wave whose distance from trough to crest was 6 cm, how would you calculate the amplitude?

Large Amplitude = High Energy

Small Amplitude = Low Energy

Page 27: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. In a transverse wave, wavelength is the distance between 2 adjacent crests (or troughs)

2. In a longitudinal wave, wavelength is the distance between 2 adjacent compressions (or rarefactions)

Page 28: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Transverse Wave

Longitudinal Wave

Compression

Rarefaction

Page 29: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Think about making rope waves again. The number of waves that you can make in 1 second depends on how quickly you move the rope. If you move the rope slowly, you make only a small number of waves each second. If you move it quickly, you make a large number of waves.

Page 30: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

The number of waves produced in a given amount of time is the frequency of the wave.

You can measure frequency by counting either the number of crests or troughs that pass a point in a certain amount of time.

Page 31: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Frequency is usually expressed in hertz (Hz).

One hertz = one wave per second

1Hz = 1/s

Page 32: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

It takes more energy to vibrate a rope quickly than to vibrate a rope slowly….thus high frequency waves carry more energy than low frequency waves.

Page 33: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. Draw a wave with an amplitude of 5 and a wavelength of 10 across a piece of graph paper.

2. Draw a wave with an amplitude of 10 and a wavelength of 4 across a piece of graph paper.

Page 34: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. If 10 centimeters is equal to one second, calculate the frequency of each wave.

2. What can you conclude about the energy contained in each wave?

Page 35: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

In general, a wave with a short wavelength carries more energy than a wave with a long wavelength.

Page 36: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Wave speed is the speed at which a wave travels.

Remember speed = distance/time Wave speed can be calculated by

measuring the distance a single crest or compression travels in a certain amount of time.

Page 37: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

The speed of a wave can change depending on the medium through which it travels….

Sound travels at 340 m/s in air, but travels at 5,200 m/s through steel…why do you think this happens?

Page 38: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

High Energy

Short wavelength

High frequency Larger amplitude

Draw one

Low Energy

Longer wavelength

Lower frequency Smaller

amplitude

Draw one

Page 39: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Draw a wave that has an amplitude of 3 and a wavelength of 2.

Label the crest, trough, resting line, amplitude and wavelength.

Page 40: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Why are boats instructed to stay at slow speed when they get close to other boats or as they approach the dock?

Page 41: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Why are we able to see the moon and planets?

Page 42: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

We have been studying how waves behave by themselves…this is not realistic. Waves are constantly interacting with other waves, running in to objects and passing through different mediums. What happens when they do this?

Page 43: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Reflection occurs when a wave bounces back after striking a barrier.

A reflected sound wave is called an echo.

An object that reflects light waves allows us to see that object.

Page 44: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Refraction is the bending of a wave as it passes from one medium to another.

Changing mediums forces the wave to change the speed at which it travels. This causes it to bend.

Page 45: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Suppose you are walking down the street and hear music playing. It seems to be coming from around the corner. There is a building on the corner blocking your view, so you can’t see who is playing the music. Why does the sound wave travel around the corner, but not the light wave?

Page 46: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Diffraction is the bending of waves around a barrier or through an opening.

Page 47: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

If the wavelength is larger than the object or opening you get lots of diffraction.

If the wavelength is smaller than the object or opening, you get very little diffraction.

Page 48: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Interference occurs when 2 or more waves occupy the same space and overlap.

There 2 categories of interference: Constructive and Destructive

Check out this link on interference

Page 49: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Constructive 1. Occurs when crests

and troughs of the waves match up.

2. Increases the amplitude of the resulting wave.

Destructive1. Occurs when the

crest of one wave overlaps with the trough of another wave.

2. Decreases the amplitude of the resulting wave.

Page 50: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Also known as a stationary wave, in this form of interference the interaction between waves gives the appearance of a wave staying in one place. However, in reality, the waves are continuing to move in both directions.

Check out this link on standing waves

Page 51: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

Do you remember what frequency is? Every object has a natural frequency

at which it will vibrate when it is disturbed.

If something nearby is vibrating at that frequency then the object will absorb that energy….to better understand, look at these examples.

Check out this video on the Tacoma Narrows Bridge.

Page 52: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. When a wave bounces back from a barrier, _____________ has occurred.

Page 53: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. When a wave bounces back from a

barrier, reflection has occurred.

Page 54: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

2. __________________ occurs when a wave bends as it passes at an angle from one medium to a difference medium.

Page 55: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

2.Refraction occurs when a wave bends as it passes at an angle from one medium to a difference medium.

Page 56: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

3. _____________ happens when two or more waves overlap.

Page 57: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

3. Interference happens when two or more waves overlap.

Page 58: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

1. Name 2 wave interactions that can occur when a wave encounters a barrier.

2. Describe what happens when a wave is refracted.

Page 59: Chapter 20. What do you think of when you hear the word wave? Write a brief description of what you know about them.

What are the characteristics of a high energy wave?


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