Transcript Optics Review
Optics Review
Exam Review 2009
Optics Review:
Types of Light Sources • INCANDESCENT – Created by glowing objects – Give off lots of heat – Inefficient – cost more to operate – Cheap to make • FLUORESCENT – Created by UV emission from mercury source – Less heat produced – Less expensive to run – More expensive to make • PHOSPHORESCENT – Glow in the dark stickers, clocks etc.
– Absorb light and then re-emit it later – Usually a greeny-yellow colour • CHEMILUMINESCENT – Chemical reaction causes light – No heat – Glow sticks • BIOLUMINESCENT – Chemiluminescence in living organisms – Fire flies, some deep sea fish
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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 R O Y G
.
B I V
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Primary Colours of Light
• Primary Additive Colours
• All colours can be made from 3 primary additive colours of
LIGHT RED + BLUE + GREEN → WHITE RED RED + BLUE → + GREEN GREEN + → BLUE MAGENTA YELLOW → 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 magenta yellow magenta + + + cyan + cyan yellow cyan → blue → → green + yellow red → black • These are used in pigments (paints, ink jet printer cartridges) • Coloured filters pull (subtract) colours to produce desired results
Optics Review
Primary Colours of Light
Example White – blue = yellow R + G + B – B = R + G yellow
+ cyan →
green R + G + G +B
→
Green *Green dominates the combination
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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
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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 RR i r Reflecting Surface
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Laws of Reflection • Example: If the angle of incidence is 45 o , what is N IR RR 45 r Mirror • Law of Reflection states that i = equal 45 o r so both • NOTE: i is between the Incident Ray and the Normal
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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:
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 • BLUE SKY Sunrises – dust and oxygen and nitrogen particles in the air reflect and refract light – oxygen and nitrogen scatter (reflect) light filtering out colours other than blue
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Properties of Lenses • 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
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Properties of Lenses • Convex lenses can • Magnify • Invert • Form real images • Concave lenses can: • Minimize • Create inverted or upright images
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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
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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 • The EYE • Eyelash • Retina • Lens • iris • Ciliary muscles • Optic Nerve • The Camera • Lens cap • Film / chip • Lens • Diaphragm • Focus ring • USB cable
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The EYE and Lenses • 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
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The EYE and Lenses • 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
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The EYE and Lenses