force, energy & communication lesson 13 & 14 waves

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Force, Energy & Communication Lesson 13 & 14 WAVES

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Page 1: Force, Energy & Communication Lesson 13 & 14 WAVES

Force, Energy & Communication

Lesson 13 & 14

WAVES

Page 2: Force, Energy & Communication Lesson 13 & 14 WAVES

Lesson objectives

Re-establish that all sound is caused by vibrations (waves)

Revise the links between pitch and wavelength; volume and amplitude.

Know a method for calculating the speed of sound

Learn the basic wave equation Measure the critical angle for a glass block

Page 3: Force, Energy & Communication Lesson 13 & 14 WAVES

WAVES – the basics

Turn to p 158 of PHYSICS text book

Page 4: Force, Energy & Communication Lesson 13 & 14 WAVES

WAVES – the basics

Waves vibrate in a regular fashion.

Page 5: Force, Energy & Communication Lesson 13 & 14 WAVES

WAVES – the basics

All sound waves are caused by vibrations.

Page 6: Force, Energy & Communication Lesson 13 & 14 WAVES

WAVES – the basics

Waves can transfer energy or information from one place to another.

Page 7: Force, Energy & Communication Lesson 13 & 14 WAVES

WAVES – the basics

While the wave may transfer information or energy, it does not transfer matter.

Page 8: Force, Energy & Communication Lesson 13 & 14 WAVES

WAVES – the basics

Nearly all the information we transfer is done by waves e.g. sound, radio, mobile phones, tv, etc

Page 9: Force, Energy & Communication Lesson 13 & 14 WAVES
Page 10: Force, Energy & Communication Lesson 13 & 14 WAVES
Page 11: Force, Energy & Communication Lesson 13 & 14 WAVES
Page 12: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the speed of sound using the echo method

Page 13: Force, Energy & Communication Lesson 13 & 14 WAVES
Page 14: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the speed of sound using the echo method

Speed = distance / time

Page 15: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the speed of sound using the echo method

Expt. no. Distance from wall (m)

No. of claps

Total distance travelled

Time (s) Speed of sound (m/s)

1 49 10

2 49 10

3 49 10

4 49 10

Page 16: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the speed of sound using the echo method

Expt. no. Distance from wall (m)

No. of claps

Total distance travelled (m)

Time (s) Speed of sound (m/s)

1 49 10 980 3.62

2 49 10 980 3.31

3 49 10 980 4.01

4 49 10 980 3.54

Page 17: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the speed of sound using the echo method Text book value for the speed of sound

through air is…..

Page 18: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the speed of sound using the echo method Text book value for the speed of sound

through air is…..330 m / s

Page 19: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

A formula you are expected to KNOW!!

Page 20: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

Turn to page 171 in the text book.

Page 21: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

The wavelength ( )of a wave depends on two things:

1 the frequency of the wave

2 the speed of the wave

Page 22: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

This can be expressed by the wave equation

Page 23: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

This can be expressed by the wave equation

speed (m/s) = frequency (Hz) X wavelength (m)

Page 24: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

This can be expressed by the wave equation

speed (m/s) = frequency (Hz) X wavelength (m)

N.B. frequency is measured in Hertz (or kilohertz). Hertz is another way of saying the number of waves in a second. E.g. 30 Hz = 30 waves every second

Page 25: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

Copy out the example calculation off p171

Page 26: Force, Energy & Communication Lesson 13 & 14 WAVES

Total Internal Reflection

Refraction happens when light is coming out of something dense like glass or water.

If the angle of the light is shallow enough, the light ray won’t come out at all but reflects back into the dense substance.

This is called total internal reflection because all the light reflects back in.

The angle over which total internal reflection occurs is called the critical angle.

Page 27: Force, Energy & Communication Lesson 13 & 14 WAVES

The Wave Equation

Page 28: Force, Energy & Communication Lesson 13 & 14 WAVES

Measuring the critical angle

Follow the instructions on your experiment sheet.

Page 29: Force, Energy & Communication Lesson 13 & 14 WAVES

HOMEWORK

Complete all questions on the sheet on “Sound waves”.

Due in next Thursday