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Light and Sound
In this unit:
1)
2)
3)
4)
5)
6)
Properties of light
Reflection
Colours
Refraction
Properties of sound
Hearing
What is light?
Light is a kind of energy.
Without light energy you could not see
anything!!!!!!!!
Light energy gives things colors, helps plants
to grow, can power solar batteries to make
electricity and is used in lasers.
Part 1 – Properties of Light
Light travels in straight lines:
How does the following experiment
prove this??????
Laser
Shadows
Shadows are places where the straight lines of
light are “blocked”:
Rays of light
Light travels VERY FAST – around
300,000 kilometers per second.
At this speed it can
go around the world 8
times in one second.
Light travels much faster than sound. For example:
1) Thunder and lightning
start at the same time,
but we will see the
lightning first.
2) When a starting pistol
is fired we see the
blast first and then
hear the bang.
Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Luminous objects
Reflectors
Dispersion of light
Dispersion of light is separating of light into
its different colours
Colour
White light is not a single colour; it is made
up of a mixture of the seven colours of the
rainbow.
We can demonstrate this by
splitting white light with a
prism:
This is how rainbows are
formed: sunlight is “split
up” by raindrops.
Prisms bend or refract
light!
The colors of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Seeing color
The color an object appears depends on the colors of
light it reflects.
For example, a red book only reflects red light:
White
light
Only red light
is reflected
We see things because they
reflect light into our eyes:
Homework
Properties of Light summary
1) Light travels in straight lines
2) Light travels much faster than sound
3) We only see things because they reflect
light into our eyes
4) Shadows are formed when light is blocked
by an object
5) Light is a form of energy like heat and
electricity
Part 2 - Reflection
Reflection from a mirror: What do you notice about
where the mirror puts the light you shine into it?
Normal
Reflected ray
Incident ray
Angle of
incidence
Angle of
reflection
Mirror
Using mirrors
Mirrors reflect all the light!
Two examples:
2) A car headlight
1) A periscope
Refraction
Refraction of light is the bending of light as it passes from
one medium to another
Refraction through a lens
Convex Lenses
cause light to
converge
or come together
because one or
both sides curve
outward.
Looking through a
convex lens
make things
look: ????
Refraction through a lens
Concave Lenses
cause light to
converge
or come together.
Looking through a
convex lens make
things look:
Applications of Refraction
Telescopes contain lenses which refract light
they allow distant objects be seen
Microscopes contain lenses which refract
light, they allow small objects be seen
Prisms refract light and are used in cameras
and binoculars
Contact lenses and spectacles refract light
and correct defective vision
Sound – The basics
We hear things when they vibrate.
If something vibrates with a high frequency (vibrates very
______) we say it has a _____ pitch.
If something vibrates with a low frequency (vibrates
______) we say it has a ____ pitch.
The lowest frequency I could hear was…
Words – slowly, low, high, quickly
Drawing sounds…
This sound wave has a
_____ frequency:
This sound wave has a
___ _frequency:
Drawing sounds…
This sound wave has a
_____ amplitude
(loud):
This sound wave has a
_____ amplitude
(quiet):
Hearing problems
Our hearing range can be damaged by several
things:
1) Too much ear wax!
2) Damage to the auditory nerve
3) Illness or infections
4) Old age (not like Mrs. Powers)
Other sound effects…
Like light, sound can be…
1) Reflected – sound reflections are called
______.
2) Refracted – this is why you might sound
strange if you try talking underwater
The Ear
Label your diagram with the following:
These bones are vibrated by the eardrum
This tube carries the sound towards the eardrum
This part is used to help us keep our balance
This part “picks up” the vibrations
This part of the ear contains many small hairs with turn
vibrations into an electrical signal
This part connects the ear to the mouth
This part “channels” the sound towards the ear drum
The Ear