Light and sound

SCIENCE 2ºESO

IES FERNADO ZÓBEL

TEACHER: JESÚS

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.

http://www.youtube.com/watch?v=Rbuhdo0AZDU

http://www.youtube.com/watch?v=jAXx0018QCc

Light and sound as waves

LIGHT WAVES SOUND WAVES

Electromagnetic spectrum

Light and sound travel in waves.

Light and sound as waves

Explanation of electromagnetic spectrum with game

http://www.bbc.co.uk/schools/gcsebitesize/

science/edexcel/electromagnetic_spectrum

/electromagneticspectrumact.shtml

Properties of light: Light sources

Sun

stars

Artificial sources

light

bulb

candle

torch

Light is a form of

electromagnetic energy. Natural sources

Properties of light: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:

Properties of light: How light travels

Light travels very quickly.

Light travels at a

speed of about

300,000 km/s or

3*10-8 m/s in a

vacuum and in air.

http://www.youtube.com/watch?v=LIvVzJ6KZpk

Properties of light: How light travels

ray of light beam of light

Light travels in a straight line.

Light travels through the small holes if these holes are aligned.

Properties of light: Shadows

shadow

shadow

penumbra

Properties of light: Eclipses

SEE ANIMATION

Solar eclipse Lunar eclipse

Solar eclipse

http://www.youtube.com/watch?v=E1B3RLf1A1s

http://www.youtube.com/watch?v=JybXE7hXpZA

http://www.youtube.com/watch?v=49O2MsT1txU

Properties of light: How light is reflected

The incident ray hits the

surface. The reflected ray

bounces off the surface.

incident

ray

reflected

ray

The light

bounces.

Properties of light: 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

Properties of light: How light is reflected. Mirrors

Concave mirror

Convex mirror

Spherical or

curved mirrors Flat mirrors

Symmetrical images

Light is refracted, or bent, when it passes from one

medium to another with a different density.

water

pencil

refracted

light

Properties of light: How light is refracted

Light bends at the

boundary of two media.

Properties of light: Lenses

Converging lens

It concentrates

the rays of light.

Diverging lens

It disperses

the rays of light.

Properties of light: Convex lenses

They are thicker in the middle than the edges.

Light moves into lens, then bends toward thickest part (middle)

Make light rays bend close together towards a central point (the thickest part)

Magnifies the object to make it look larger than the original object

It might also make the image appear to be upside down, this happens when the

light rays cross.

Properties of light: Concave lenses

They are thinner in the middle than at the edges and curve inwards.

Light enters and bends toward thickest part (ends)

Make the light rays spread out and make objects look smaller.

Used to correct near-sightedness (can’t see far away). Help make

details look clearer

The image always stays upright.

Properties of light: Dispersion

Remember:

If white light passes

through a prism, it splits

up into the different

colours. This is called

dispersion

Can you recognize

the spectrum in

nature? Yes, in the

colours of a rainbow

Properties of light: Dispersion II

Prism

Range of wavelengths

Visible light

Ult

ravio

let

lig

ht In

fare

d lig

ht

Visible light waves are the only electromagnetic waves

visible to the human eye.

Properties of light: Making colours

Colours of light

Colours of pigment

red

green blue

yellow

magenta

cyan

Objects reflect the colour of light that we

can see and absorb all the other colours.

Colour mixing

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

http://www.youtube.com/watch?v=xH8mT2IQz7Y

The qualities of sound

Loudness (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. his question is not trivial, because

As far as I can determine, "pitch"

is translated as "tono" in Spanish.

que permite ordenarlos de graves

However, "tone" is best translated

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

Properties of sound : 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.

Properties of sound: Reflect sound.Echoes and Sonar

Fishing boats use sonar to detect shoals of fish.

reflected sound

emitted sound

Bats and dolphins use echolocation.