u12 light sound
TRANSCRIPT
ESSENTIAL NATURAL SCIENCE 2Unit 12
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Light and sound
CONTENTS
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ESSENTIAL NATURAL SCIENCE 2Unit 12
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Contents
Sound
Sound as waves Properties
Qualities
The qualities of sound
Reflection
Echoes and reverberationSonar
Light and sound
Perception
The ear
Light
Light as wavesLight sourcesLight and objects
Properties
How light travels
Shadows
Types of shadowsEclipses
Reflection
How light is reflectedMirrors
Refraction
How light is refractedLenses
Colour
Seeing coloursMaking colours
Perception
The eyeCameras
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Eclipses
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Light and sound as waves
Light sources Light and objects How light travels Shadows
How light is reflected
Mirrors LensesHow light is refracted
Seeing colours Making colours The eye Properties of sound
Echoes and reveberations
The earSonarThe qualities of sound
Cameras
Links
Light and sound
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Light waves
Light and sound as waves
Sound waves
wavelength
trough
crest
Wave characteristics Units of measurement
frequency hertz (Hz)
wavelength metre (m)
Light and sound travel in waves.
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Light sources
Sun
stars
Artificial sources
light bulb
candle
torch
Light is a form of electromagnetic energy. Natural sources
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Light and objects
Transparent
They allow light to travel through.
Translucent
They absorb some light, and they allow some to travel through.
Opaque
They do not allow light to travel through.
Objects, materials and substances can be:
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How light travels
ray of lightbeam of light
Light travels in a straight line.
Light travels at a speed of about 300,000 km/s in a vacuum and in air.
Light travels through the small holes if these holes are aligned.
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Shadowsshadow
shadow
penumbra
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Eclipses
SEE ANIMATION
Solar eclipseLunar eclipse
Solar eclipse
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Eclipses
Solar eclipseLunar eclipse
Solar eclipse
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How light is reflected
The incident ray hits the surface. The reflected ray bounces off the surface.
incident ray
reflected ray
The light bounces.
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How light is reflected
The incident ray hits the surface. The reflected ray bounces off the surface.
incident ray
reflected ray
The light bounces.
normal ray
reflecting surface
angle of incidence
angle of refection
incident ray reflected ray
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Mirrors
Concave mirror
Convex mirror
Spherical or curved mirrors
Flat mirrors
Symmetrical images
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Light is refracted, or bent, when it passes from one medium to another with a different density.
water
pencil
refracted light
How light is refracted
Light bends at the boundary of two media.
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Lenses
Converging lens
It concentrates the rays of light.
Diverging lens
It disperses the rays of light.
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Seeing colours
Prism
Range of wavelengths
Visible light
Ult
ravi
ole
t lig
ht In
fared lig
ht
Visible light waves are the only electromagnetic waves visible to the human eye.
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Making colours
Colours of light
Colours of pigment
red
greenblue
yellow
magenta
cyan
white light
Objects reflect the colour of light that we can see and absorb all the other colours.
Colour mixing
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The eye
Light enters through the cornea
The iris regulates the amount of light that enters.
The pupil increases or decreases depending on the amount of light.
An inverted image forms on the retina
The optic nerve transmits the image to the brain.
The lens focuses images.
HOW A CAMERA WORKS
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Cameras
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Light enters through the shutter.
The lens focuses images.
The image forms on the film or sensor.
The diaphragm regulates the amount of light that enters.
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Properties of sound
Sound is a form of mechanical energy produced by the vibration of an object.
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Properties of sound
Sound is a form of mechanical energy produced by the vibration of an object.
THE SPEED OF SOUND IN DIFFERENT MEDIA
Air (at 20 ºC) 340 m/s
Water (at 0 ºC) 1,500 m/s
Iron (at 20 ºC) 5 ,130 m/s
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The qualities of sound
Intensity depends on the amplitude of the sound waves.
Pitch depends on the frequency of the sound waves.
Tone allows you to identify the source of a sound which has the same frequency and intensity.
soft sound
loud sound
low pitched sound
high pitched sound
SEE INTENSITITES OF SOME SOUNDS.
CLICK ON THE SOUND ICON TO LISTEN TO THE SOUND.
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The qualities of sound
Intensity depends on the amplitude of the sound waves.
Pitch depends on the frequency of the sound waves.
Tone allows you to identify the source of a sound which has the same frequency and intensity.
soft sound
loud sound
low pitched sound
high pitched sound
SEE INTENSITITES OF SOME SOUNDS.
CLICK ON THE SOUND ICON TO LISTEN TO THE SOUND.
Intensity of some sounds
Leaves rustling 20 dB
Whispering 30 dB
Inside a library 40 dB
Inside an office 50 dB
Normal conversation 60 dB
City traffic 80 dB
Motorcycle 90 dB
Rock concert 110 dB
Thunder 120 dB
Jet taking off 140 dB
Rocket blasting off 180 dB
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Echoes and reverberations
Distance (metres)
0 0.1
34 0
Time (seconds)
17
Speed: 340 m/s
ECHO REVERBERATION
An echo is heard at more than 17 metres.
A reverberation is heard at less than 17 metres.
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Sonar
Fishing boats use sonar to detect shoals of fish.
reflected sound
emitted sound
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The ear
Frequency (Hz)
Infrasound(below 20 Hz)
Ultrasound (above 20,000 Hz)
The ear can hear sounds which have a frequency of 20 Hz to 20,000 Hz.
sound wave
The eardrum vibrates when sound waves reach it.
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Links
Sound energyhttp://www.worsleyschool.net/science/files/sound/energy.html
What is soundhttp://antonine-education.co.uk/Physics_GCSE/Unit_3/Topic_5/topic_5.htm
Soundhttp://www.bbc.co.uk/schools/ks3bitesize/science/physics/sound_intro.shtml
Light, reflection & refractionhttp://acept.asu.edu/PiN/mod/light/reflection/pattLight1.html
Light and opticshttp://camillasenior.homestead.com/optics.html
Light activitieshttp://galileo.phys.virginia.edu/classes/620/Optics_Activities.html
Materials and lighthttp://jc-schools.net/write/sci/light_files/frame.htm
Optics for kidshttp://www.opticalres.com/kidoptx_f.html
Light and soundhttp://www.sciencejoywagon.com/physicszone/09waves/