Transcript Optics Lesson # 1

Optics Lesson # 1
The Electromagnetic Spectrum
The Sun
• The sun produces huge amounts of
energy, and some of this energy is in the
form of light.
• The sun’s light travels through the vacuum
of space and reaches earth, providing
enough energy to heat the earth’s surface
and allow photosynthesis to occur on land
and in water.
Properties of Light
•Light travels at very high speeds – so fast that if
something was travelling at the speed of light, it
could circle around the Earth 7.5 times in one
second!
•Light always travels in straight lines.
•Light does not need to travel through a medium (a
physical substance used for energy transfer) – it
can travel through the vacuum of space.
•Light energy is transferred through radiation.
•Light shows wave-like properties.
Parts of a Wave
The Electromagnetic Spectrum
•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.
•Visible light, along with other types of waves such as
radio waves, X-ray, and UV radiation are all part of an
energy classification system called the
electromagnetic spectrum.
•Waves on the left of the spectrum are longer and
slower (lower frequency), such as radio waves,
microwaves, and infrared waves. Waves on the right
of the spectrum are shorter and quicker (higher
frequency), such as ultraviolet waves, x-ray waves,
and gamma ray waves.
Seeing Light
•Visible light is in the centre of the spectrum,
and is the only light we can see with the naked
eye.
•Infrared light can be seen with “night-vision”
goggles.
•Ultraviolet light can be seen through “black
lights.”
•Scientists have been able to explore life on
earth as well as deep space with the discovery
of different forms of light energy.
Video
•The Electromagnetic Spectrum
The EMS
Types of Waves
Type of Wave
Radio Waves
Microwaves
Infrared Light
Visible Light
Ultraviolet Light
X-Rays
Gamma Rays




















Use/Phenomena
Signals: AM/FM radio, TV, cell phones, internet
RADAR
Used in MRI scans for soft tissue images
Microwave ovens
Telecommunications
Speed detection – police “radar” guns
Remote controls
Heat detection – thermographs
Motion sensors
Food warming (heating lamps at restaurants)
Human vision
Rainbows
Lasers
Tanning beds – skin tan/burn
Kills bacteria in food and water
Medical imaging – penetrate bone
Airport luggage scanners
Cancer treatment
Sterilize medical equipment
Reactions of black holes and stars
Visible Light
•Visible light is also called “white light.”
•Visible light is composed of a continuous sequence of colours,
making up the visible spectrum.
•7 distinct colours can be seen – red, orange, yellow, green, blue,
indigo, and violet (ROY G. BIV).
•Red is the least energetic (closest to infrared waves), and violet is
the most energetic (closest to ultraviolet waves) part of the visible
spectrum.
Colour Theory
•If the three primary colours of light are added together, white
light is produced. These colours are red, blue, and green
(not yellow!).
•Remember, colours of light are just waves of different
energy (frequency) – they are not the same as mixing two
paint colours together.
•If two of the primary colours are added together, secondary
colours are produced.
•Red + Blue = Magenta
•Blue + Green = Cyan
•Green + Red = Yellow
Production of Light
•Most people think light can only come from the Sun –
because it radiates its own light.
•This is called a luminous light source.
•Light actually enters your eyes from all objects that
you see – it is being reflected.
•Most objects are seen this way, as they are
non-luminous light sources.