Transcript Light and Optics

Grade 10 Academic Science
Light and Optics Unit
Unit Organization
Light and
Optics
Production and
Reflection
Refraction
Lenses and
Optical Devices
Light is Weird
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Light is a form of energy visible to the human eye
Light does not need a medium to travel
Light sometimes displays properties of waves and sometimes
displays properties of particles
Light travels at 300 000 000 m/s
Light takes 8.3 minutes to reach the Earth
Light travels in straight lines if travelling in the same medium
Life on Earth would not exist without light
The Electromagnetic Spectrum
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An electromagnetic wave is a wave that has both electric and magnetic
parts, does not require a medium, and travels at the speed of light
There are many different types of electromagnetic waves
- i.e. x-rays, microwaves, radio waves
Visible light is an electromagnetic wave that the human eye can detect
Visible spectrum of colours: red, orange, yellow, green, blue, indigo, violet
Refer to page 466 in your textbook
for more examples of the
electromagnetic spectrum
Visible Light and the Spectrum
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White light is composed of all the colours of the rainbow.
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ROYGBIV
 red-orange-yellow-green-blue-indigo-violet
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A glass prism is capable of separating the colours because each
colour travels through the prism at a slightly different speed.
Why we see things!
We see things because light hits our eyes from all objects.
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Luminous
 Something that provides it’s own light
 i.e. sun or lightbulb
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Non-luminous
 Something that reflects or absorbs light
 i.e. moon, mirror
Sources of Light - Natural
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Sunlight (solar radiation)
Stars (burning balls of gas)
Lightning
Core of the Earth (magma)
Bioluminescent objects
Sources of Light – Electric Powered
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Incandescent lights
 Emitting light because of high temperature
Light emitting diodes (LED’s)
Electric Discharge
 Use of electricity to excite a gas
Fluorescent Lights
 filled with mercury vapour
Sources of Light - Combustion
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Candles
Fire
Oil lamps
Sources of Light - Chemical
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Chemiluminescence
 Light produced by a chemical reaction
 i.e. glow sticks
Bioluminescence
 Light produced by a living thing
 i.e. fireflies, glow worms, plankton, fish, jellyfish
Phosphorescence
 Light produced for some time after receiving energy from another
source
 i.e. hands on a watch
Fluorescence
 Light produced while receiving energy from another source
 i.e. black light
Incandescent Light
Electricity passes through a
filament, causing it be
become hot and give off
light
Light Emitting Diodes (LED’s)
Electric Discharge
Electricity causes the gas to glow
E.g. neon sign
Fluorescent Light
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Fluorescent light
 filled with mercury vapour
 current + mercury = UV light
 UV light absorbed by fluorescent coating on inner
surface of tube
Black light
Watch
Plankton
Glowsticks
Firefly
Glow worms
Deep-Sea Fish