By the end of chapter 4 you will be able to: Learning Goals By the end of chapter 4 you will be able to: Recognize that waves carry energy Describe ways in which water waves can explain properties of light Explain why a prism separates white light into different colours Describe properties and uses of electromagnetic waves. (c) McGraw Hill Ryerson 2007

Waves with different properties can be sued in different ways Why it is important We can see and hear the world around us because of the energy carried by waves. Waves with different properties can be sued in different ways Electromagnetic waves can be sued to make different kinds of images in the world around us. (c) McGraw Hill Ryerson 2007

What is light? (c) McGraw Hill Ryerson 2007

Light is a kind of energy that travels in waves. What is light? Light is a kind of energy that travels in waves. What are some sources of light? Intro to Light Video Ted Ed: https://www.youtube.com/watch?v=O0PawPSdk28 Light is a form of energy. We cannot feel light. We can only see it. Light comes from both natural and manmade sources. Sun, lamp, phosphorescence Not: mirrors, moon (c) McGraw Hill Ryerson 2007

Sources of light https://www.youtube.com/watch?v=BUYeQa_-ojk (c) McGraw Hill Ryerson 2007

Light is part of the Electromagnetic Spectrum Electromagnetic Spectrum 2min https://www.youtube.com/watch?v=m4t7gTmBK3g Electromagnetic Spectrum of Radiation: (c) McGraw Hill Ryerson 2007

To describe the electromagnetic spectrum, we need to understand properties of waves. (c) McGraw Hill Ryerson 2007

How can we describe Waves? Light behaves like a wave (c) McGraw Hill Ryerson 2007

Energy is the capacity to apply a force over a distance. 4.1 Properties of Waves A wave is a disturbance or movement that transfers energy through matter or space. Examples of waves include: water waves, sound waves, and microwaves. Energy is the capacity to apply a force over a distance. A force is a push or a pull on an object. See page 134 (c) McGraw Hill Ryerson 2007

A crest is the highest point on a wave. Features of a Wave A crest is the highest point on a wave. A trough is the lowest point on a wave. The wavelength is the distance, in meters, for one complete cycle of the wave. Crest to crest or trough to trough. The amplitude is the height of a wave crest or depth of a trough, as measured from its rest position. Identify each of the lettered parts of the wave. See pages 135 - 136 (c) McGraw Hill Ryerson 2007

Frequency is usually measured in hertz (Hz). Frequency is the number of repetitive motions, or oscillations , that occur in a given time. Frequency is usually measured in hertz (Hz). When the frequency of a wave increases the wavelength decreases. This is called an Inverse Relationship. This is called an Inverse Relationship See page 136 (c) McGraw Hill Ryerson 2007

Bill Nye: Waves https://www.youtube.com/watch?v=R89dJP5v1Tg (c) McGraw Hill Ryerson 2007

Homework Workbook p52-53 (c) McGraw Hill Ryerson 2007

Activity Catch a Wave p139 (c) McGraw Hill Ryerson 2007

Calculating Frequency Frequency can be calculated using the following equation: frequency = cycles/seconds Use the above equation to find the frequency for each of the following: a) A hummingbird flaps its wings 120 times in 3 seconds. b) A DVD spins 35 times in 7 seconds. Go to the next slide to view the answers See page 138 (c) McGraw Hill Ryerson 2007

Calculating Frequency Frequency can be calculated using the following equation: frequency = cycles/seconds Use the above equation to find the frequency for each of the following: a) A hummingbird flaps its wings 120 times in 3 seconds. (40 Hz) b) A DVD spins 35 times in 7 seconds. (5 Hz) Take the Section 4.1 Quiz See page 138 (c) McGraw Hill Ryerson 2007

Two types of waves that travel through a medium are: The matter that waves travel through is called a medium (can be solid, liquid, gas) Some waves such as light waves, can travel through space where there is no medium. Two types of waves that travel through a medium are: Transverse wave – matter in the medium moves perpendicular to direction of the wave. Compression wave – matter in the medium moves parallel to direction of the wave. Transverse wave Compression wave See page 137 (c) McGraw Hill Ryerson 2007

Waves transfer energy through matter or space. Summary Waves transfer energy through matter or space. Amplitude is the height of a waves crest or depth of a wave trough, as measured from its rest position. A wavelength is the distance over which the wave repeats. As the wavelength decrease, the frequency increases. Waves can differ in how much energy they carry and in how fast they travel. (c) McGraw Hill Ryerson 2007

Homework Read pages 134-137 Answer CYU p143 #1, 2, 3, 4, 7, 8. (c) McGraw Hill Ryerson 2007

EMS video 5 min https://www.youtube.com/watch?v=cfXzwh3KadE (c) McGraw Hill Ryerson 2007

What is light? In a nutshell, 4.38min https://www.youtube.com/watch?v=IXxZRZxafEQ Also need to know about waves and EMS (c) McGraw Hill Ryerson 2007