U12 Light Sound

Light and sound CONTENTS RESOURCES

Contents Sound Sound as waves Properties Qualities The qualities of sound Reflection Echoes and reverberation Sonar Light and sound Perception The ear Light Light as waves Light sources Light and objects Properties How light travels Shadows Types of shadows Eclipses Reflection How light is reflected Mirrors Refraction How light is refracted Lenses Colour Seeing colours Making colours Perception The eye Cameras

Resources Eclipses Light and sound as waves Light sources Light and objects How light travels Shadows How light is reflected Mirrors Lenses How light is refracted Seeing colours Making colours The eye Properties of sound Echoes and reveberations The ear Sonar The qualities of sound Cameras Links Light and sound

Light waves Light and sound as waves Sound waves wavelength trough crest Light and sound travel in waves. Wave characteristics Units of measurement frequency hertz (Hz) wavelength metre (m)

Light sources Sun stars Artificial sources candle torch Light is a form of electromagnetic energy. Natural sources light bulb

Light and objects Transparent They allow light to travel through. Objects, materials and substances can be: Translucent They absorb some light, and they allow some to travel through. Opaque They do not allow light to travel through.

How light travels ray of light beam 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.

Shadows shadow shadow penumbra

Eclipses Solar eclipse Lunar eclipse Solar eclipse SEE ANIMATION

Eclipses Solar eclipse Lunar eclipse Solar eclipse GO BACK

How light is reflected The incident ray hits the surface. The reflected ray bounces off the surface. incident ray reflected ray The light bounces.

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 X

Mirrors Concave mirror Convex mirror Spherical or curved mirrors Flat mirrors Symmetrical images

How light is refracted Light bends at the boundary of two media. Light is refracted, or bent, when it passes from one medium to another with a different density. water pencil refracted light

Lenses Converging lens It concentrates the rays of light. Diverging lens It disperses the rays of light.

Seeing colours Prism Visible light waves are the only electromagnetic waves visible to the human eye. Range of wavelengths Visible light Ultraviolet light Infared light

Making colours Colours of light Colours of pigment white light Objects reflect the colour of light that we can see and absorb all the other colours. Colour mixing red green blue yellow magenta cyan

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

Cameras 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. GO BACK

Properties of sound Sound is a form of mechanical energy produced by the vibration of an object.

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 X

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.

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 X

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.

Sonar Fishing boats use sonar to detect shoals of fish. reflected sound emitted sound

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.

Links Sound energy http:// www.worsleyschool.net/science/files/sound/energy.html What is sound http://antonine-education.co.uk/Physics_GCSE/Unit_3/Topic_5/topic_5.htm Sound http://www.bbc.co.uk/schools/ks3bitesize/science/physics/sound_intro.shtml Light, reflection & refraction http://acept.asu.edu/PiN/mod/light/reflection/pattLight1.html Light and optics http:// camillasenior.homestead.com/optics.html Light activities http://galileo.phys.virginia.edu/classes/620/Optics_Activities.html Materials and light http://jc-schools.net/write/sci/light_files/frame.htm Optics for kids http:// www.opticalres.com/kidoptx_f.html Light and sound http://www.sciencejoywagon.com/physicszone/09waves/

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U12 Light Sound

by Alkor on Jan 04, 2010

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U12 Light Sound — Presentation Transcript