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

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 R O Y G

.

B I V

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 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

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 RR i r Reflecting Surface

Optics Review:

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

Optics Review:

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

Optics Review:

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

Optics Review:

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 • The EYE • Eyelash • Retina • Lens • iris • Ciliary muscles • Optic Nerve • The Camera • Lens cap • Film / chip • Lens • Diaphragm • Focus ring • USB cable

Optics Review:

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

Optics Review:

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

Optics Review:

The EYE and Lenses