StopwatchStopwatch Graph HomeGraphHome Behaviour of Waves Lesson 1: Types of Waves Lesson 2: Wave Speed Reflection Lesson 3: Refraction Total Internal

$Page 1: StopwatchStopwatch Graph HomeGraphHome Behaviour of Waves Lesson 1: Types of Waves Lesson 2: Wave Speed Reflection Lesson 3: Refraction Total Internal$
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Behaviour of WavesLesson 1: Types of WavesLesson 2: Wave Speed

ReflectionLesson 3: Refraction

Total Internal ReflectionLesson 4: Refraction in WaterLesson 5: Refractive IndexLesson 6: Refraction in WaterLesson 7: Refractive IndexLesson 8: DiffractionLesson 9: Transmitting InformationLesson 10: Sound


Syllabus Double AwardProperties of waves describe longitudinal and transverse waves in ropes, springs and water where appropriate state the meaning of amplitude, frequency, wavelength and period of a wave recall that waves transfer energy and information without transferring matter recall and use the relationship between the speed, frequency and wavelength of a wave:

wave speed = frequency × wavelength v = f × λ

use the relationship between frequency and time period: frequency = 1 / time period f = 1 / T

use the above relationships in different contexts including sound waves and electromagnetic waves Light and sound recall that light waves are transverse waves which can be reflected and refracted recall that the angle of incidence equals the angle of reflection construct ray diagrams to illustrate the formation of a virtual image in a plane mirror describe experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms recall and use the relationship between refractive index, angle of incidence and angle of

refraction n = sin (i) / sin (r)

describe an experiment to determine the refractive index of glass, using a glass block describe the role of total internal reflection in transmitting information along optical fibres and in prisms recall and use the relationship between critical angle and refractive index

sin c = 1 / n recall that sound waves are longitudinal waves which can be reflected recall that the frequency range for human hearing is 20 Hz – 20 000 Hz describe how to measure the speed of sound in air by a simple direct method


Syllabus Separate ScienceProperties of waves describe longitudinal and transverse waves in ropes, springs and water where appropriate state the meaning of amplitude, frequency, wavelength and period of a wave recall that waves transfer energy and information without transferring matter recall and use the relationship between the speed, frequency and wavelength of a wave:

wave speed = frequency × wavelength v = f × λ

use the relationship between frequency and time period: frequency = 1 / time period f = 1 / T

use the above relationships in different contexts including sound waves and electromagnetic waves understand that waves can be diffracted through gaps or when they pass an edge, and that the extent of diffraction depends on

the wavelength and the physical dimension of the gapLight and sound recall that light waves are transverse waves which can be reflected, refracted and diffracted recall that the angle of incidence equals the angle of reflection construct ray diagrams to illustrate the formation of a virtual image in a plane mirror describe experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms recall and use the relationship between refractive index, angle of incidence and angle of refraction

n = sin(i) / sin(r) describe an experiment to determine the refractive index of glass, using a glass block describe the role of total internal reflection in transmitting information along optical fibres and in prisms recall the meaning of critical angle c recall and use the relationship between critical angle and refractive index

sin c = 1 / n understand the difference between analogue and digital signals recall that sound waves are longitudinal waves which can be reflected, refracted and diffracted recall that the frequency range for human hearing is 20 Hz – 20 000 Hz describe how to measure the speed of sound in air by a simple direct method understand how an oscilloscope and microphone can be used to display a sound wave use an oscilloscope to determine the frequency of a sound wave and appreciate that the pitch of a sound depends on the

frequency of vibration appreciate that the pitch of a sound depends on the frequency of vibration of the source appreciate that the loudness of a sound depends on the amplitude of vibration


Types of Waves 04/19/23

Aims To define the properties of waves To identify the types of waves

Starter: True or False1) Sound travels faster than light2) Sound travels faster in solid objects than in liquids or

air3) Echoes are caused by sound waves bouncing of walls4) Sound waves are caused by the vibration of

molecules5) Sound travels faster at the top of Mt. Everest6) Light waves bounce off walls


A Wave Waves transfer energy from one place to

another The disturbance moves along the wave not

the particles


A wave in the sea: • disturbance is molecules of water going up and down• medium = water


A Mexican Wave

The Disturbance is the people going up and down. The medium is the crowd.


Frequency = 1 Hertz

Frequency = 1.4 Hertz

Frequency = 0.5 HertzTen second timer

Count the number of complete vibrations in ten seconds and then work out the frequency of this wave


Note that the waves are carrying energy from oneplace to another but the water particles are nottransferred.

previous next


Frequency Number of waves per second Either passing one point or generated Symbol: f Units: Hz (s-1)


Period This is the duration of a wave How long it takes for one wave to occur Symbol: T Units: s


time Heart monitor

1 second

We often need to analyse waveforms produced by scientific instruments. For example:- A Cathode Ray Oscilloscope (CRO)is used to monitor heartbeats.

0.5seconds

Steady Steve

David Deadman

Helen Heart-attack


Pictures of waves (waveforms)

2 tuning fork

1 mains voltage waveform

3 Ultrasonic scanner

0.02 seconds

2.5milliseconds (0.0025seconds)

10 micro seconds

(0.00001 seconds)Work out the frequency for these 3 waveforms

Stopwatch Graph HomePictures of waves (waveforms)

Which animals made these sounds?

Stopwatch Graph HomePictures of waves (waveforms)

2 Baby crying

1 Cow

3 Bat

0.004 seconds

0.5milliseconds (0.0005seconds)

10 micro seconds

(0.00001 seconds)


Wavelength


Wavelength The length of one complete wave peak to peak or trough to trough Symbol: λ Units: m


A B

C D

EF

G

Which of the points is exactly one wavelength away from point A? Answeris E

The next 5 tasks will test to see if you have understood the idea of wavelength


A B C D E F G H I J L M O P Q R S T U V WXK N

1 Match the highlighted letter to one which is exactly one wavelength away from it.














Amplitude maximum disturbance caused by a wave measured from the middle to a peak or trough symbol: a units: m


Questions about amplitudeMatch the waveforms to the sounds

A B C

D F

1 an echo2 a crescendo

4 a strong regular heartbeat3 a weak regular heartbeat

5 a symbol being struck

12345

Click foranswers


Transverse Waves


Transverse Wave


Transverse Wave The disturbance is perpendicular to the direction of

movement Example Light


Longitudinal Waves


Longitudinal Waves The disturbance is parallel to the direction of

movement Aka: pressure, compression waves Example sound Sketch on board



Wave Behaviour recap

Aim To define the properties of waves To identify the types of waves

Wave Speed 19/04/23

Aim: To calculate the speed of waves To Revise Reflection

Starter:• Draw a transverse wave in rough and label the

wavelength and amplitude• The frequency of a wave is 5 Hz what is it’s

Period? (check back in your book if you need to)


•How fast the wave is travelling•Symbol v•Units m/s


ENERGYspeed

VIBRATIONS

The speed is how fast the disturbance travels (how fast the energy is transferred)


speed

ENERGY

speed

Notice that both waves have the same speed but different wavelengths and frequencies. The wave equation can explain this mathematically.


Calculating the Speed of Wave

Speed = DistanceTime

An explosion happens 1000m away and takes 3 seconds to reach you what is the speed of sound?Speed = Distance

TimeSpeed = 1000

3 = 333 m/s


Wave speed, wavelength and frequency arerelated by the wave equation


The Wave Equation

The wave equation relates the speed of the wave to its frequency and wavelength:

Wave speed (v) = frequency (f) x wavelength ()

in m/s in Hz in m

V

fWorksheet


Practice Questions:Write out the variables (ie frequency = …) and the equations used

1. A water wave travels through a pond with a frequency of 5Hz and they are 10 m apart. How fast are they travelling?

2. Ricky hears a thunderclap that makes his ear drum vibrate at 165 Hz. The wavelength of the sound is 2 m how fast is the sound wave travelling?

3. Hannah sings an A, she knows the wavelength of the sound wave is 1.5m. How many times does her vocal chords vibrate per second? (hint: you need the answer to question 2)

4. Hannah plays another note on her guitar, the string vibrates with a frequency of 300 Hz what is the duration (the period) of each vibration of the string?

5. Jon has been running his heart is beating 180 times a minute. What is the frequency and period of his heart beats.

6. Jack throws a stone into the centre of a pond. The pond has a radius of 4m. He notices that it takes 2 seconds for the wave to reach the edge. He thinks the wavelength of the ripple is about 1m. What is the frequency of his ripple? What is the period of the ripple?

7. Purple light has a wavelength of around 6x10-7m. If its frequency is 5x1014 Hz what is the speed of light?

8. Red light travels at the same speed. Work out its frequency if its wavelength is about 4x10-7m.






Reflection

Incident ray

Normal

Reflected ray

Angle of incidence

Angle of reflection

Mirror

Angle of incidence = Angle of reflection

Movie Worksheet



monitor

transducer

Ultrasoundgenerator

high frequencyelectrical signal

changes theelectricalsignal into an ultrasonic pulse

Echoes are changed back into electricalsignals. These areprocessed and imaged on the monitor

Contactgel


monitor

Ultrasoundgenerator

Click to start the scan

(4.5 months)

•and partly reflected ultrasonic waves from boundaries can be processed to produce an image of the foetus

•speed of ultrasound inside the body

•time for the ultrasound to travel


Wave Speed recap

Aim: To calculate the speed of waves To Revise Reflection


Refraction 19/04/23

Aims: To demonstrate refraction To explain the cause of refraction To observe total internal reflectionStarter:Why does the magic trick of the Disappearing Coin work?

Home


Refraction at a Boundary


Refraction is when waves ____ __ or slow down due to changing _________. A medium is something that waves will travel through.

Refraction

Movie


Refraction through a glass block:

Method:1) Place a rectangular block of glass or Perspex in the

middle of a page on your book and draw around it.2) Draw a normal line a third along one of the long sides3) Draw a line at 20° to this normal to mark the incident

ray.4) Use a ray box and single slit to shine a ray of light

along the path you have marked for the incident ray.5) Mark two dots on the path of the refracted ray with a

pencil. Join the dots with a ruler to show the path of the refracted ray.

6) Remove the block and draw the path taken by the ray of light inside the block.



This wheel slows first

The car travels

slower on the sand

than tarmac

The cars direction changes

This wheel continues to move fast

The cars direction changes

This wheel speeds up



Refraction through a glass block:

Wave slows down and bends towards the normal due to

entering a more dense medium

Wave speeds up and bends away from the normal due to entering a less dense

medium

Wave slows down but is not bent, due to

entering along the normal

Movie Worksheet


What is total internal reflection?Method:

1) Place a semi circular block of glass or Perspex in the middle of a sheet of plain paper and draw around it.

2) Draw a normal line at the middle of the flat side

3) Use a ray box and single slit to shine a ray of light to the normal line

4) Change the angle of the ray of light until total internal reflection if found.

5) Then change the angle until the light is refracted along the horizontal side.

6) Mark two dots on the path of the refracted ray with a pencil. Join the dots with a ruler to show the path of the refracted ray.

6) Measure the critical angle


Total internal reflection – simulation


Why is angle of incidence important?

If the angle of incidence is smaller than the critical angle, then the light ray is refracted.

If the angle of incidence equals the critical angle, then the light ray is refracted along the boundary.

If the angle of incidence is greater than the critical angle, then total internal reflection occurs.


Is the critical angle always the same?The critical angle is the smallest angle of incidence at which total internal reflection occurs.

Diamond has the lowest critical angle at 24°.

49°

42°

41°

24°

water

acrylic plastic

glass

diamond

Critical angleMaterial

Different materials have a specific value for the critical angle:

This means that diamond reflects more light than the other materials and accounts for its characteristic sparkle.


Total Internal Reflection


Optical fibres do not have to be straight to carry light and can even carry light around corners.

How do optical fibres carry light?

Light travels through the Perspex rod, and optical fibres, by aprocess called total internal reflection.

This curved Perspex rod shows how light travels in an optical fibre.


Total Internal Reflection recap

Aims: To describe the effect of the critical angle To know some uses of the critical angle

Home


Refraction in Water 19/04/23

Aim Experimentally determine the effect of water

depth on speed and establish if there is a relationship between the two


Experiment: Wave SpeedYou are expected to: Write a method Draw a graph of results Write a analysis / conclusion Write an evaluation

Overview: Work out what you are going to do before you start You need at least 6 different depths for a graph The effect is only noticed on small depths (mm not cm) You need to make sure that the effect is not drowned out

by your reaction time You need to make sure that one mistake does not ruin your

results


Refractive Index 19/04/23

Aim Experimentally determine the refractive index of

glass describe an experiment to determine the refractive

index of glass


Finding the Refractive Index of GlassMethod: Draw around the semi circular block. Draw a normal line in the middle of the straight edge of the

block. Draw Incident lines every 10° from 0° to 70° Use a ray box to send incident rays into the semi circular box

and mark out the refracted rays. Measure the refracted angles

Results: Create a table of the incident, refracted angles, sin i, and sin r. Plot a graph of sin i (x) against sin r (y)


Work To Do:

Results: Create a table of the incident, refracted angles, sin

i, and sin r. Plot a graph of sin i (x) against sin r (y)

Analysis What shape is your graph? Add an extra column to your table with the heading

refractive index (n) n = sin(i) ÷ sin (r) Calculate the gradient of your graph The critical angle of glass (c) = 41° Calculate sin(c)


Equations to Learn:

A measure of how much light is refracted (bends) in a material. glass n = 1.6 Diamond n = 2.5

Refractive index (n): n = sin i

sin rCritical Angle (c):

sin c = 1n

Critical angle

refracted angle

incident angle


Refractive Index recap

Aim Experimentally determine the refractive index of

glass describe an experiment to determine the refractive

index of glass


Diffraction 19/04/23

Aims: To define diffraction To see reflection and refraction in water waves

Starter:Worksheet

Separate Science


Separate Science


Barrier

Water wavesare reflectedby the barrier

Separate Science


Separate Science


Deep water

Shallow water

The waves slow downwhen they reach the shallow water

Ripple tankmodel

The wavelength getsshorter

But the frequency stays the same

Can you understandwhat is happening here? HINT remember the wave equation

Separate Science


Deep water

Shallow water

Water wavesIf the waves reach theshallow water at anangle the waves stillslow down.

The waves alsochange direction. We call this effect refraction.

Separate Science


Separate Science


•Diffraction is the spreading out of waves at edges and gaps.

•All types of waves can be diffracted.•The amount of diffraction is affected by the

size of the gap and the wavelength.

Separate Science


Separate Science


Separate Science


Separate Science


Small amount of spreading (diffraction)

The wavelength of the waves is much smallerthan the size of the gap

Separate Science


The wavelength is thesame size as the gapso there is very goodspreading (diffraction)

Separate Science


For EdgesLong wavelengths diffract more than shortwavelengths.

For GapsThe wavelength should be the same sizeas the gap to get good diffraction.

Separate Science


Typical frequency = 440Hertz

Speed of sound in air = 330m/s

Speed = wavelength x frequency

Work out the wavelength of these sound waves

Wavelength = speed/frequency

Wavelength = 330/440 = 0.75metres

About the same size as the width of a door

Separate Science



To get spreading (diffraction) of the lightthe gap it passes through has to be verysmall-because the wavelength of light isvery small

Separate Science


Separate Science


Separate Science


The aerial is on a poleto try and improve thereception of radio waves.

Separate Science


Separate Science


Separate Science


There is very little diffraction of short wavelength radio waves when they pass between two hills

Separate Science


Long wavelength radio waves are more likely to be diffracted when they pass between hills and are more likely to be detected by the aerial.

Separate Science


Separate Science


Copy and complete this email:To [email protected] are having difficulty with the signal strength on your short wave radio because…

Helpful words/phrases to use: long wavelengthshort wavelength, diffracted, gap, edge.Copy and complete the diagrams to illustrate youranswer.

Separate Science


A

B

C

D

Which of these show how rays are(a) reflected? (b) diffracted at a gap?(c) refracted? (d) diffracted at an edge?

Separate Science


Which of these show how waves are(a) reflected? (b) diffracted at a gap?(c) refracted? (d) diffracted at an edge?

Separate Science


Diffraction recap

Aims: To define diffraction

Home

Worksheet


Transmitting Information 19/04/23Aim To explain the difference between analogue and

digital signals

Separate Science


What is an analogue signal?

Most of the signals sensed by humans are analogue signals. Everyday examples include sound, light and temperature.

An analogue signal may have any value within a continuous range.

time

volt

ag

e

Separate Science


What is a digital signal?Modern communication systems carry information from analogue signals as digital signals.

A digital signal only contains two values: ‘0’ (off) and ‘1’ (on). These are used to encode analogue information.

time

cu

rren

t

Separate Science


Converting analogue to digitalSeparate Science


Why do analogue signals lose quality? All types of signals lose strength as they travel. This is called attenuation and means that signals often have to be amplified so they can be used.

original attenuated amplified

Signals can also pick up noise (interference).

Separate Science


Why don’t digital signals lose quality?Digital signals also lose strength and need to be amplified.

attenuated amplifiedoriginal

regenerated

threshold

Separate Science


Digital vs Analogue Analogue signals are continually changing. Digital signals are either zero or one This means if the signal gets distorted you can work

out the digital signal (it should either be zero or one) but you will not be able to tell the original analogue signal


Analogue or digital?Separate Science


Communications – matching activitySeparate Science


Opinions on analogue and digitalSeparate Science


What’s in a cable of optical fibres?Separate Science


How do messages travel along optical fibres? Separate Science


Sending messagesSeparate Science


Optical fibres – true or false?Separate Science


Transmitting Information recapAim To explain the difference between analogue and

digital signals


Sound 19/04/23Aim Measure the Speed of Sound Know the human hearing range


100,000

10,000

1,000

100

10

1

0human dog elephantbat mouse dolphin

•Which animals hear the lowest and the highest frequencies?•Which animal has the largest hearing range?

frequency(Hz)


Sound The human hearing range is from 20 – 20 000 Hz Its best range is at age 8 the pitch of a sound depends on the frequency of vibration of

the source the loudness of a sound depends on the amplitude of vibration

BA C DWhich sound is:•The quietest•The loudest•The highest•The lowest


100 m

00:0000

START

00:0034

STOP

1. When you see the cymbals crash, press START.2. When you hear the cymbals crash, press STOP.

This investigation to calculate the speed of sound should be carried out in a quiet open space.

Speed of sound experiment


Experiment distance (m)

time(s)

speed(m/s)

1

Look at the results of the sound experiment.

=294 m/s distance tim

e

speed =

=100

0.34

100 0.34 294

Speed of sound experiment – results table

How are these values used to estimate the speed of sound?


Speed of Sound Experiment Write a method for our speed of sound experiment Write out the results Calculate the speed of sound Are our results accurate? Why might they not be?


Movie CB

Documents

StopwatchStopwatch Graph HomeGraphHome Behaviour of Waves Lesson 1: Types of Waves Lesson 2: Wave Speed Reflection Lesson 3: Refraction Total Internal