light - nbed.nb.caweb1.nbed.nb.ca/sites/asd-w/pams/teachers/audio/optics... · 2019. 2. 25. ·...
TRANSCRIPT
Light
- Overview of light
- Properties of light
- Luminous and non-luminous
objects
- History of light
- The electromagnetic spectrum
- Prisms
- Colour & Colour Blindness
Where does light come from?
The SUN!!
• The sun is a star located 1.50 x 108 km, or 1 Astronomical Unit, away from Earth. • It provides energy in the form of light through a process called nuclear fusion. • Nuclear fusion occurs when two atoms that naturally repelled each other are pulled together by a superior force and the atoms fuse together. • Nuclear fusion produces energy that reaches us as heat and light.
• The sun provides the energy that enables life on Earth.
What The Heck Is Light
Properties of Light
• Light travels in straight lines:
Laser
• Light travels VERY FAST – 3.0X108m/s
= 300,000 kilometres per second.
At this speed it can go around the world 7.5 times in one second.
The Strangeness of Light
• The speed of light (c) is constant
• Nothing moves faster than the speed of light
• Anything with mass cannot travel at the speed of light
• 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.
• We see things because they reflectlight into our eyes:
Homework
Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Shadows
Shadows are places where light is “blocked”:
Properties 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
Fun Science Light Video
History
• Unlike heat and sound energy which requires a medium (a physical substance) to move, light does not
• Light is transferred through radiation in a vacuum at the speed of light (3.0X108 m/s)
• Light is classified as an Electromagnetic Wave
Modern electromagnetic waves
• Today we have identified many types of electromagnetic waves which makes up our electromagnetic spectrum
The Electromagnetic Spectrum video
Modern View Continued
As we decrease wavelength, we increase frequency and energy
The Visible Light Spectrum
• Different colours have different wavelengths!
The Surprising Universe
• Today Scientists use different portions of the electromagnetic spectrum to collect and analyze data about stars and galaxies
• This provides them with completely different views compared with using visible light only
The Surprising Universe
Essential Knowledge, Skills, and Processes
• Analyze the effects of a prism on white light and describe why this occurs. Explain why a rainbow occurs.
Answer: Different
colours have different
wavelengths which
bend differently as
they pass through the
prism
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.
The colours of the rainbow:
• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet
Prisms
• What happens when you place two prisms next to each other?
Simulation
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:
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
Colour Adding and Subtracting Simulation
Seeing 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
A white hat would reflect all seven colours:
A pair of purple pants would reflect purple light (and red and blue, as purple is made up of red and blue):
Purple light
White
light
Using coloured light
• If we look at a coloured object in coloured light we see something different. For example, consider a soccer uniform:
White
light
Shorts look blue
Shirt looks red
• In different colours of light this uniform would look different:
Red
lightShirt looks red, why?
Shorts look black, why?
Blue
light
Shirt looks black, why?
Shorts look blue, why?
Using filters• Filters can be used to “block” out different colours of light:
Red Filter
Magenta Filter
Colour Blindness
• The tricky thing about colour blindness is that many people don’t know they are colour blind until they get tested
• (40% of colour blind pupils currently leaving secondary school are unaware that they are colour blind)
How many animals are
there?
6!
• Red Green Colour Blindness is caused by a gene on the X chromosome therefore, since males have 1 X and 1 Y while females carry 2 X’s, this issue is predominately found in males (7-10% of the overall population) and is very rarely seen in females.
• For these people, they cannot see red and green light.
• Blue Colour Blindness is equally unlikely for both males and females as the deficient gene is found on chromosome 7. These people can’t see blue colour light
• In both these cases the problem isn't as straight forward as not seeing blue, red or green light. If what they are looking at contains these colours, they will not be seen.
What is Colour Blindness
Light and Colour - Bill Nye Video