Section 3 - The Behavior of Waves Chapter 10 - Waves Section 3 - The Behavior of Waves

Chapter 10 Section 3 – What You’ll Learn - page 301 Before you read - write the reading’s objectives in this space: 1 – _______________________________________ ____________________________________________________________________________________ 2 – _______________________________________ 3 - ________________________________________ 4 - ________________________________________ __________________________________________

Chapter 10 Section 3 – What You’ll Learn - page 301 Before you read - write the reading’s objectives in this space: 1 – State the law of reflection. 2 – Explain why waves change direction when they travel from one material to another. 3 – Compare and contrast refraction and diffraction. 4 – Describe how waves interfere with each other.

Dolphins and bats both use something called echolocation to find where objects are. Using the space below: either draw a diagram or write how you think this works. 1

Dolphins and bats both use something called echolocation to find where objects are. Either draw a diagram or write how you think this works in this space. The animal emits a sound, usually at a very high frequency, which bounces off an object and returns as an echo. Click image for hyperlink 1

What is a reflection?___________________________ __________________________________________ ALL types of waves can be reflected. Light, sound, even water. 2

Waves that strike a surface then bounce off. What is a reflection? Waves that strike a surface then bounce off. ALL types of waves can be reflected. Light, sound, even water. 2

What is the law of reflection? ______________________________________________________________________________________________________________________________ All reflected waves obey this law. 3

What is the law of reflection? The angle of incidence is equal to the angle of reflection. All reflected waves obey this law. 3

What is refraction? ________________ ______________________________ The angle of refraction varies by frequency, causing these light colors to emerge at different angles from a prism. 4

What is refraction? The bending of a wave caused by a change in its speed as it moves from one medium to another. The angle of refraction varies by frequency, causing these light colors to emerge at different angles from a prism. 4

Refraction of Light in Water When light waves travel from water to air, they speed up and bend away from the normal. When light waves travel from air to water, they slow down and bend toward the normal. 5

What is diffraction? ________________________________ _______________________________________________ So What is the difference between diffraction and refraction then?___________________________________________ ______________________________________________________________________________________________ 6

What is diffraction? When an object causes a wave to change direction and bend around it. So What is the difference between diffraction and refraction then? The difference is that refraction occurs when waves pass through an object, while diffraction occurs when waves pass around an object. 6 After they pass through the opening, the waves spread out.

The bending of a wave caused by a change in its speed as it moves from one medium to another. Moves from water onto sandbar. Waves also can be diffracted when they pass through a narrow opening between sandbars. The sand bar causes a wave to change direction and bend around it.

____________________________ If the obstacle is larger than the wavelength, the waves do not diffract as much. In fact, if the obstacle is much larger than the wavelength, almost no diffraction occurs. You’re walking down the hallway and you can hear sounds coming from the lunchroom before you reach the open lunchroom door. Why can you hear the sound waves but not see the light waves while you’re still in the hallway? ____________________________ _______________________________________________ 7

If the obstacle is larger than the wavelength, the waves do not diffract as much. In fact, if the obstacle is much larger than the wavelength, almost no diffraction occurs. You’re walking down the hallway and you can hear sounds coming from the lunchroom before you reach the open lunchroom door. Why can you hear the sound waves but not see the light waves while you’re still in the hallway? The wavelengths of sound waves are similar in size to a door opening. Sound waves diffract around the door and spread out down the hallway. 7 Light waves have a much shorter wavelength. They are hardly diffracted at all by the door.

What is interference? __________________________________________________________________________________________________________________________________ 8 Acoustics http://www.youtube.com/watch?v=MCzMjLYj2QQ&feature=related

When two or more waves overlap and combine to form a new wave What is interference? When two or more waves overlap and combine to form a new wave 8

What is constructive interference?__________________ ________________________________________________________________________________________________________________________________________________________________________ What is the amplitude of constructive interference? ____________________________________________________________________________________ 9

What is constructive interference What is constructive interference? When the crests of two or more transverse waves arrive at the same place at the same time and overlap. What is the amplitude of constructive interference? The new amplitude is equal to the sum of the amplitudes of the original waves. (Add the old ones together.) 9

What is destructive interference?__________________ ___________________________________________________________________________________________________________________________ How do I find the amplitude of this new wave? __________________________________________________________________________________ 10

What is destructive interference What is destructive interference? When the crests of one transverse wave meet the troughs of another transverse wave. How do I find the amplitude of this new wave? The amplitude of the new wave is the difference between the amplitudes of the waves that overlapped. (Subtract the waves.) 10

What are standing waves? ______________________ ___________________________________________________________________________________________________________________________ 11

What are standing waves What are standing waves? A special type of wave pattern that forms when waves equal in wavelength and amplitude, but traveling in opposite directions, continuously interfere with each other. The places where the two waves always cancel are called nodes. Shown along the blue line in the diagram below. 11

Myth Busters – Can the Human Voice Break Glass? What is resonance?____________________________ ____________________________________________________________________________________ How can resonance cause an object to break ?__________ ______________________________________________________________________________________________________________________________ Myth Busters – Can the Human Voice Break Glass? About 17 min Part 1 Part 2 Part 3 12

Myth Busters – Can the Human Voice Break Glass? What is resonance? The process by which an object is made to vibrate by absorbing energy at its natural frequencies. How can resonance cause an object to break? An object that vibrates too strongly can break. Myth Busters – Can the Human Voice Break Glass? About 17 min Part 1 Part 2 Part 3 12

Section Check 3 Question 1 State the law of reflection. 13

Question 1 Answer 3 State the law of reflection. Section Check 3 Question 1 State the law of reflection. Answer According to the law of reflection, the angle of incidence is equal to the angle of reflection. 13

Question 2 __________ is the bending of a wave caused by a change in its speed as it moves from one medium to another. A. Diffraction B. Diffusion C. Refraction D. Reflection 14

Question 2 __________ is the bending of a wave caused by a change in its speed as it moves from one medium to another. A. Diffraction B. Diffusion C. Refraction D. Reflection Answer The answer is C. The greater the change in speed is, the more the wave bends. 14

Question 3 Which is the means by which you can hear around corners? A. diffraction B. diffusion C. reflection D. refraction 15

Question 3 Which is the means by which you can hear around corners? A. diffraction B. diffusion C. reflection D. refraction Answer The answer is A. Diffraction occurs when an object causes a wave to change direction and bend around it. 15