Light 3 - Colours PPT.pdf colours physics

Lights

1. Light 3 Colours

2. Agenda
1.Understand convex and concave
lenses
2.Learn about white light and dispersion
3.Primary and secondary colours
4.Learn how light is interpreted by our
eyes and how light is absorbed by
materials
Page 98 - 99

3. Review

4. What is refraction of light?
Refraction is the bending of light as it passes
from one medium into another.
Review

5. What two things change the angle of refraction?
1) The angle of the light hitting the boundary between
two mediums.
2) The difference in density between the two mediums.
Review

6. When light passes from a less dense to a more
dense medium...
A.The speed of light increases and the light bends
away from normal.
B.The speed of light decreases and the light bends
towards normal.
Light Reflection

7. Vocabulary

8. Vocabulary
Prism
Disperse
Spectrum
A transparent figure used for
dispersing white light into a light
spectrum.
1
2
3
Distribute or spread over a wide area.
A band of colours as seen in a rainbow.
1
3
2
Wavelength
4 The distance between successive crests of a
wave.
4

9. Vocabulary
Frequency
Lens
Visible Light
Outline or surface curved like the exterior of
a circle.
1
2
3
Transparent substance with curved sides for
converging or dispersing light rays.
Wavelengths of light that are visible to the
human eye.
4
3
2
Convex
4 The rate at which something occurs, or is
repeated, over a period of time.
1

10. Vocabulary
Concave
Disperse
Converge
When lines scatter, or spread out, over
a wide area.
1
2
3
Outline or surface curved inwards like the
interior of a circle.
When lines meet at a point.
3
1
2

11. Lenses and Optics

12. What are Lenses?
Lenses are a piece of glass, or other transparent material, with
curved sides for converging or dispersing light rays.
There are two basic types of lenses: Concave and Convex
Concave
•Concave Lenses cave inward
(thinner in the middle).
•They take light in from the
direction of its focal point and
spread it outward.
•Used in nearsighted glasses.
Concave lenses disperse light rays.

13. Convex
What are Lenses?
Lenses are a piece of glass, or other transparent material, with
curved sides for converging or dispersing light rays.
•Convex Lenses bulge outward
(thicker in the middle).
•They take light that is spread
out and focus it so that the
reflected light creates a focal
point.
•Used in farsighted glasses.
Convex lenses converge light rays.

14. Focal Point
The focal point is where light rays come together,
before or after, reflection or refraction.
•The focal point is important for creating focused images
(images that are crisp and clear).

15. Lenses and Optical Instruments
Can you think of any examples of instruments that use
mirrors and lenses to help us see things better?
•Optical instruments use a series of mirrors or/and
converging and diverging lenses to reflect and bend
light in order to see objects that are far away or close up.

16. Light and Colours

17. Issac Newton's Prism Experiment
In 1665 Sir Isaac Newton was studying at Cambridge
University and wanted to understand more about light.
•It was previously believed that light
creates colours but that colours do
not exist within white light.
•Newton, however, believed that the
colours of the spectrum already
existed inside white light. This was a
hypothesis, but he wanted to test it.

18. Issac Newton's Prism Experiment
•To test his hypothesis,
Newton darkened his
room and cut a small
hole in the window to
allow a beam of light to
shine through and into a
prism.
•From the prism, Newton
shone the spectrum of
light against his wall that
looked like a rainbow.
The experiment

19. Issac Newton's Prism Experiment
Newton was right! But he believed that if he could
reverse this effect, it would prove that the colours exist
within white light.
•To test his second
hypothesis Newton
placed another prism
upside-down in front of
the first prism.
He was right again!

20. Issac Newton's Prism Experiment
•The band of colors from the first prism combined again when
directed through the second prism and was transformed back
into white light.
Newton was the
first to prove that
white light is made
up of all the colors
that we can see.

21. The Visible Spectrum
The visible spectrum is a small part of the Electromagnetic
Spectrum, and the only part the human eye can detect (see).

22. Visible Light
•Visible light is made up of many
different wavelengths which our
eyes can detect.
•Each color has a different
wavelength of light.
•When all the waves are together,
they make white light.
•This is why white light is described
as poly-chromatic (many colours).

23. Dispersing White Light
•From studying Newton's experiment, we know that white light
can be split to make the colours of the rainbow.
Dispersion is when white light is broken into colours,
such as through a prism or in a rainbow.

24. Dispersing White Light
•The colours that make up white light are called the spectrum and
the order of the colours in the spectrum is always the same.
•To remember the order of the colours, you can use the
phrase: “Richard Of York Gave Battle In Vain”, or think about
ROY G BIV.

25. •The colours made by mixing
two primary colours are
called the secondary colours;
magenta, yellow and cyan.
•When the primary colours mix
together they make white light.
There are 3 primary colours of light that can be mixed in
different amounts to make all other colours.
•The primary colours are red,
green and blue.
Primary and Secondary Colours

26. How we see Colours

27. The Human Eye
Eyes are very complex, using light and distance to help view the
world around us.
•All light that enters the human
eye will be directed toward the
focal point, toward the retina at
the back of the eye.
•The retina has special cells that
are photo-receptors which help
us to see light.

28. The Human Eye
There are 3 types of
cones to detect colour
- one for each of the
primary colours.
The rods help us see at
night, but they can only
detect light and dark.
The retina contains special photo-receptor cells called rods and
cones that help us to see colours.

29. Absorption and Reflection
•The colours we see are a result of the wavelengths of the
visible spectrum that are reflected back into our eyes.
•Objects appear to be different colours because the molecules
absorb different wavelengths of light.
•The colour of light that is reflected determines the color of
the item.

30. Colour Filters
Colour filters are sheets of transparent materials that absorbs
some of the wavelengths of colours from white light, while
allowing others to pass through.
Colour filters are used to create coloured light:
A red filter absorbs all
colours…
A blue filter absorbs all
colours…
A green filter absorbs all
colours...
…apart from red light
…apart from blue light
…apart from green light

31. …apart from red and green
…apart from green and blue
…apart from red and blue
Colour Filters
•Colour filters can also be used for secondary colours.
•When filtering secondary colours, they will will absorb all
colours expect those needed to make the secondary colour.
A magenta absorbs all
colours…
A cyan filter absorbs all
colours…
A yellow filter absorbs
all colours...

32. How do we see Colours
Let's watch a quick video to see how this works.

33. Textbook Practice
In your Exploring Science Physics Textbook
pages 98 & 99 complete questions 1 - 7

35. Online Simulation

36. Colour Simulation
In breakout room groups, let’s explore light and colours.
●You will have 5 minutes to try
the online simulator.
●Change the amount of each
coloured light and see how it
affects what colours we see.
●See how colour filters work.
Open the online simulator

37. Review Quiz

38. Review
Match the statements to the type of lens:
Convex lens
Concave lens
Converging
Dispersing
A
B

39. What order are the colours in white light (the spectrum)?Red, orange, yellow, green, blue, indigo, violet.
Review

40. What are the primary colours?Red, green and blue.
Review

41. Black objects...
A.Absorb all the colours of light.
B.Absorb only black light.
C.Reflect all the colours of light.
Review

42. 1.Convex and concave lenses
2.White light and dispersion
3.How light is interpreted by our eyes
4.How light is absorbed by materials
5.Working with colours and filters
What did we do today?

43. Bring your Physics textbook.
Next week:
We will study ‘Electricity: Series and Parallel’

44. End of Class