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Light and Sound

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Light and Sound In this unit: Properties of light Reflection Colors Refraction Properties of sound Hearing What is light? Light is a kind of energy. – PowerPoint PPT presentation

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Title: Light and Sound


1
(No Transcript)
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Light and Sound
  • In this unit
  • Properties of light
  • Reflection
  • Colors
  • Refraction
  • Properties of sound
  • Hearing

3
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.

4
Part 1 Properties of Light
  • Light travels in straight lines
  • How does the following experiment prove this??????

5
  • Shadows

Shadows are places where the straight lines of
light are blocked
6
  • Light travels VERY FAST around 300,000
    kilometers per second.

At this speed it can go around the world 8 times
in one second.
7
  • Light travels much faster than sound. For example
  • 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.

8
  • We see things because they reflect light into our
    eyes

Homework
9
  • 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
10
Properties of Light summary
  • Light travels in straight lines
  • Light travels much faster than sound
  • We only see things because they reflect light
    into our eyes
  • Shadows are formed when light is blocked by an
    object
  • Light is a form of energy like heat and
    electricity

11
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 reflection
Angle of incidence
Mirror
12
  • The Law of Reflection

Angle of incidence Angle of reflection
In other words, light gets reflected from a
surface at ____ _____ angle it hits it.
The same !!!
13
Clear vs. Diffuse Reflection
  • Smooth, shiny surfaces have a clear reflection

Rough, dull surfaces have a diffuse
reflection. Diffuse reflection is when light is
scattered in different directions
14
Absorbing Light
  • Stopping light is called absorption.
  • When light hits most objects, some of the light
    bounces off and the rest is absorbed.
  • Smooth shiny objects reflect most of the light.
    Dull objects absorb most of the light that hits
    them an reflects the rest.
  • What you see when you look at it is the light
    that bounces off of it.

15
Absorption
  • Opaque Objects-Reflects or absorbs all the light.
    You cannot see through opaque objects. Can you
    name some opaque objects?
  • Translucent Objects-Reflects and absorbs some
    light. You can see a blurry or fuzzy image when
    you look through it. Can you name some opaque
    objects?
  • Transparent- Does not reflect or absorb light.
    You see a clear image when you look through it.
    Can you name some transparent objects?

16
Using mirrors
  • Mirrors reflect all the light!
  • Two examples

2) A car headlight
1) A periscope
17
Color
  • White light is not a single color 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!
18
The colors of the rainbow
  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet

19
Adding colours
  • White light can be split up to make separate
    colours. These colours can be added together
    again.
  • The primary colours of light are red, blue and
    green This is different than paint primary
    colors!!!

Adding blue and red makes magenta (purple)
Adding blue and green makes cyan (light blue)
Adding all three makes white again
Adding red and green makes yellow
20
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
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A pair of purple trousers would reflect purple
light (and red and blue, as purple is made up
of red and blue)
Purple light
A white hat would reflect all seven colors
White light
22
Using colored light
  • If we look at a colored object in colored light
    we see something different. For example,
    consider a football kit

Shirt looks red
White light
Shorts look blue
23
  • In different colors of light this kit would look
    different

Red light
Shirt looks red
Shorts look black
Shirt looks black
Blue light
Shorts look blue
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Some further examples
25
Using filters
  • Filters can be used to block out different
    colours of light

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Red
White
Blue
Green
Magenta
Yellow
Cyan
27
Refraction (http//www.brainpop.com/science/seeall
/)
Refraction is when waves ____ __ or slow down due
to travelling in a different _________. A medium
is something that waves will travel through.
When a pen is placed in water it looks like
this In this case the light rays are slowed
down by the water and are _____, causing the pen
to look odd. The two mediums in this example are
______ and _______. (Words speed up, water,
air, bent, medium)
28
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THE LENS
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CONVEX-BICONVEX
  • Convex Lenses cause light to
  • converge
  • or come together because one or both sides curve
    outward.
  • Looking through a convex lens make things look
    ????

32
CONCAVE-BICONCAVE
Concave Lenses cause light to converge or come
together. Looking through a convex lens make
things look
33
THE LENS YOU USE EVERYDAY
34
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
35
Drawing sounds
This sound wave has a _____ frequency
This sound wave has a ___ _frequency
36
Drawing sounds
This sound wave has a _____ amplitude (loud)
This sound wave has a _____ amplitude (quiet)
37
Hearing problems
  • Our hearing range can be damaged by several
    things
  • Too much ear wax!
  • Damage to the auditory nerve
  • Illness or infections
  • Old age (not like Mrs. Powers)

38
Other sound effects
  • Like light, sound can be
  • Reflected sound reflections are called ______.
  • Refracted this is why you might sound strange
    if you try talking underwater

39
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
40
The Ear
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