light_ presentation with slidesssss .ppt

light

1. Sound and Light 1
Sound and Light
The
Nature of
Light

2. WavesWaves
•Any form of disturbance that Any form of disturbance that
propagates. It conist of vibrations propagates. It conist of vibrations
which transfer from one place to which transfer from one place to
anotheranother

3. WavesWaves
May be longitudinalMay be longitudinal
Or transverseOr transverse

4. WavesWaves

5. Waves travel through a medium Waves travel through a medium
such as:such as:
water
air
solids

6. Wave Wave
PropertiesProperties
reflection
refraction
interference
diffraction

7. Wave PropertiesWave Properties
1. Diffraction: when 1. Diffraction: when
a wave enters a a wave enters a
narrow opening.narrow opening.

8. 2. REFRACTION
•Light waves REFRACT when they move
from one transparent material to another,
such as from air to glass or to water.
•TO REFRACT IS TO BEND.

9. 3. Reflection3. Reflection
- Bouncing back of waves as they hit the
barrier.
Incident ray
Normal
Reflected ray
Angle of
incidence
Angle of
reflection
Mirror

10. Clear vs. Diffuse ReflectionClear 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

11. 4. Interference- overlapping of waves
Constructive interference = crest meets crest
Destructive interference = crest meets trough
Constructive Destructive

12. Properties of LightProperties of Light
Light travels in straight lines:
Laser

13. Light travels VERY FAST – around
300,000 kilometres per second.
At this speed it can
go around the world 8
times in one second.

14. 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
smoke first and then
hear the bang.

15. We see things because they
reflect light into our eyes:
Homework

16. Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Luminous objectsReflectors

17. Shadows
Shadows are places where light is “blocked”:
Rays of light

18. Properties of Light summaryProperties of Light summary
1)Light travels in straight lines
2)Light travels much faster than sound
3)We see things because they reflect light
into our eyes
4)Shadows are formed when light is blocked
by an object

19. Sound and Light 19
Dispersion
The effect in
which white light
separates into
different colors
Due to changes
in wave speed of
the different
colors

20. ColourColour
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.

21. Notice that the colored bands in a prism are
always arranged in the same order. This
happens because the prism bends each
color at a specific angle.
Red
Orange
Yellow
Green
Blue
Indigo
Violet

22. The colours of the rainbow:The colours of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet
RED- lowest frequency- travel fastest-
bend the least
VIOLET- highest frequency- travel
slowest- bend the most

23. Adding coloursAdding 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:
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

24. Seeing colourSeeing colour
The colour an object appears depends on the colours
of light it reflects.
For example, a red book only reflects red light:
White
light
Only red light
is reflected

25. A white hat would reflect all seven colours:
A pair of purple trousers would reflect purple light
(and red and blue, as purple is made up of red and blue):
Purple light
White
light

26. Using coloured lightUsing coloured light
If we look at a coloured object in coloured
light we see something different. For
example, consider a football kit:
White
light
Shorts look blue
Shirt looks red

27. In different colours of light this kit would look different:
Red
light
Shirt looks red
Shorts look black
Blue
light
Shirt looks black
Shorts look blue