Optics Review

1. Optics Review Exam Review 2009

2. 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

3. 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 ROYG. BIV

4. 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!

5. 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

6. 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

7. 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 

8. 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

9. 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

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

11. Optics Review: Laws of Refraction IR • 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) N

12. 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 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

13. 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

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

15. 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

16. 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)

17. Optics Review: The EYE

18. Optics Review: The EYE

19. 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

20. 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

22. 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

23. Optics Review: The EYE and Lenses