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

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: Properties 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

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 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

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 Optics Review: Laws of Reflection IRRR ir N Reflecting Surface

Example: If the angle of incidence is 45 o, what is the angle of reflection? Law of Reflection states that  i =  r so both equal 45 o NOTE:  i is between the Incident Ray and the Normal Optics Review: Laws of Reflection IRRR 45r N Mirror

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) Optics Review: Laws of Refraction IR N

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: Refraction

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

Convex lenses can Magnify Invert Form real images Concave lenses can: Minimize Create inverted or upright images Optics Review: Properties of Lenses

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

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