Optics Review
Exam Review 2009
Optics Review:
Types of Light Sources
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INCANDESCENT
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FLUORESCENT
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PHOSPHORESCENT
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CHEMILUMINESCENT
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BIOLUMINESCENT
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Created by glowing objects
Give off lots of heat
Inefficient – cost more to operate
Cheap to make
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Created by UV emission from mercury source
Less heat produced
Less expensive to run
More expensive to make
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Glow in the dark stickers, clocks etc.
Absorb light and then re-emit it later
Usually a greeny-yellow colour
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Chemical reaction causes light
No heat
Glow sticks
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Chemiluminescence in living organisms
Fire flies, some deep sea fish
Optics Review:
Properties of Light
• Light travels in straight lines called RAYS
• Light is a form of energy and travels in
WAVES
• “White” Light can be refracted into the
VISIBLE SPECTRUM
ROY G. BIV
Optics Review:
Primary Colours of Light
• Primary Additive Colours
• All colours can be made from 3 primary additive colours of
LIGHT
RED + BLUE + GREEN → WHITE
RED + BLUE → MAGENTA
RED + GREEN → YELLOW
GREEN + BLUE → CYAN
Technologies that use this: TV’s, spotlights, movie theatres
THE HUMAN EYE!
Optics Review
Primary Colours of Light
• Primary Subtractive Colours of Light
• Take White light and subtract one primary colour and we
have a Subtractive Colour
Ex: White – blue = yellow
magenta + cyan → blue
magenta + yellow → red
yellow + cyan → green
magenta + cyan + yellow → black
• These are used in pigments (paints, ink jet printer
cartridges)
• Coloured filters pull (subtract) colours to produce desired
results
Optics Review
Example
White
R+G+B
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Primary Colours of Light
blue
– B
yellow + cyan
R + G + G +B
=
=
yellow
R+G
→ green
→ Green
*Green dominates the combination
Optics Review:
EMR
• Electromagnetic Radiation is a spectrum of
wave energies and includes VISIBLE light
• Waves have WAVELENGTH (), FREQUENCY(), and
AMPLITUDE (A)
• From shortest to greatest frequency
(least energy --------------------------------------------------------- most energy)
Radio – Micro – Infrared – VIS – UV – X-Rays – Gamma Rays
Longest  ----------------------------------------------- shortest 
Optics Review:
Uses of EMR
• RadioWaves
– TV, radio, cell phones
• Microwaves
– Microwave ovens – cooking food
– Telecommunications
• Infrared
– Remote controls
– Thermal imaging
• UV
– Tanning (also causes sun burns and skin damage)
– Heating lamps – fast food, spas
• X-Rays
– Doctors and dentists use to see bones/teeth
• Gamma Rays
– Doctors use to target and kill cancer cells
Optics Review:
Laws of Reflection
• Light travels in straight lines called RAYS
• Light bounces or reflects off of hard, shiny surfaces like a
mirror
• Law 1: The Angle of Incidence (i) = the
Angle of Reflection (r)
• Law 2: The Incident Ray (IR), Reflected
Ray (RR), and the Normal (N) are in the
same plane
N
IR
i
r
RR
Reflecting Surface
Optics Review:
Laws of Reflection
• Example: If the angle of incidence is 45o, what is
the angle of reflection?
N
IR
45 r
RR
Mirror
• Law of Reflection states that i =  r so both
equal 45o
• NOTE: i is between the Incident Ray and the
Normal
Laws of Refraction
• Light “bends” or refracts when light moves
at an angle from one medium to another
• Law 1: The refracted ray bends
towards the normal if light
enters a denser medium (air →
water)
• Law 2: The refracted ray
bends away from the normal if
light enters a less dens medium
(water → air)
IR
N
Optics Review:
Optics Review:
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Refraction
When light enters water, light is “bent”
This causes optical illusions
Double images
Images of objects where they are not
• REFRACTION and REFLECTION ALSO CAUSE:
• Rainbows
• Sun dogs (rainbow like circles around the sun on the very
cold days)
• Sunsets and Sunrises – dust and oxygen and nitrogen
particles in the air reflect and refract light
• BLUE SKY – oxygen and nitrogen scatter (reflect) light
filtering out colours other than blue
Optics Review:
• Lenses are shaped pieces
of plastic or glass that
refract light
• Convex Lenses: thicker in
middle – converge or
focus light
• Concave Lenses: thicker
on edge – diverge or
spread light
Properties of Lenses
Optics Review:
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Properties of Lenses
Convex lenses can
Magnify
Invert
Form real images
Concave lenses can:
Minimize
Create inverted or upright images
Optics Review:
Properties of Mirrors
• Lenses are shaped pieces of plastic or glass that
refract light
• Convex Mirrors (fisheye): Create virtual, upright,
smaller images
• Used in side mirrors, security mirrors
• Concave Lenses: can create many different types
of images depending upon placement
• Used for vanity/makeup mirrors - magnifying
Optics Review:
The EYE
• The eye is the organ responsible for sight
• The retina has two types of cells:
• RODS – sensitive to light
• See in shades of gray
• CONES – sensitive to colour
• RED, GREEN & BLUE (the three primary colours)
Optics Review:
The EYE
Optics Review:
The EYE
Optics Review:
• The EYE
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Eyelash
Retina
Lens
iris
Ciliary muscles
Optic Nerve
The EYE
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The Camera
Lens cap
Film / chip
Lens
Diaphragm
Focus ring
USB cable
Optics Review:
• Farsightedness –
lens too flat, the
image produced by
the lens is too far
past the retina
• Correction – use a
convex lens to
converge the image
on the retina
The EYE and Lenses
Optics Review:
• Nearsightedness –
lens too curved; the
image produced by the
lens is too far forward
of the retina
• Correction – use a
concave lens to
diverge the image on
the retina
The EYE and Lenses
Optics Review:
The EYE and Lenses