Post on 13-Mar-2016
description
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.
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
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.