1. 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.
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2. 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.
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3. What is light?
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4. 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:
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
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5. Sources of light https://www.youtube.com/watch?v=BUYeQa_-ojk
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6. Light is part of the Electromagnetic Spectrum
Electromagnetic Spectrum 2min
Electromagnetic Spectrum of Radiation:
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7. To describe the electromagnetic spectrum, we need to understand properties of waves.
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8. How can we describe Waves?
Light behaves like a wave
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9. 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
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10. 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
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11. 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
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12. Bill Nye: Waves https://www.youtube.com/watch?v=R89dJP5v1Tg
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13. Homework
Workbook p52-53
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14. Activity
Catch a Wave p139
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15. 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 seconds.
b) A DVD spins 35 times in 7 seconds.
Go to the next slide to view the answers
See page 138
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16. 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 seconds. (40 Hz)
b) A DVD spins 35 times in 7 seconds. (5 Hz)
Take the Section 4.1 Quiz
See page 138
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17. 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
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18. 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.
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19. Homework Read pages 134-137 Answer CYU p143 #1, 2, 3, 4, 7, 8.
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20. EMS video 5 min https://www.youtube.com/watch?v=cfXzwh3KadE
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21. What is light? In a nutshell, 4.38min
Also need to know about waves and EMS
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