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SNC2D – Physics: Light and Geometric Optics
Introduction to Optics
What is Optics? “optics” comes from a Greek word meaning “appearance” or “look”
Branch of physics that studies the properties and behaviour of light
Opening activity: With a partner, take a few minutes to brainstorm as many optical devices and
applications of light as you can that impact our lives and society. Remember to think of items
related to the areas of medicine, scientific investigation, environmental or practical everyday
items. Write some of them down in the space below.
Medical applications
Scientific Applications
Endoscopes, x-rays, ultrasound, laser eye
surgery, dental UV, CAT
Microscopes, telescopes,
Everyday items
Tv, flashlight, cell phones, glasses, contact
lenses, computer monitors, lighting, bar code
Rainbows, fireflies, electric eels, angler fish,
northern lights, light pollution, fire, sun, flying
birds (blinded by office lights), solar power
What is light and how is it produced?
Light is a visible form of energy, whose properties and behaviour can be modeled as
waves.(Wave Model of Light)
Light is a form of electromagnetic radiation, a wave pattern of electrical and magnetic fields
that can travel through empty space.
Other forms of electromagnetic radiation include invisible waves such as radio, infrared,
ultraviolet and x-rays.
Light is produced when electrons in atoms absorb energy and jump to a higher energy level, and
then return to their stable ground state, emitting the energy as a visible wave.
SNC2D – Physics: Light and Geometric Optics
Sources of Light (pp. 470-476, Science Perspectives 10, Nelson )
Source of Light
Light emitted from a hot body (a heated filament) due to its
Bioluminescence: (Greek “bios” for "living" and the Latin
“lumen” for "light")
Incandescent light bulb (very
inefficient, ~95% energy used as
Fireflies, glow worms, angler fish
Light produced and emitted by a living organism as the
result of a chemical reaction in which chemical energy is
converted to light energy.
Glowsticks, “Glo” necklace
Light produced from a chemical reaction without a rise in
Light produced by the absorption of radiation at one
wavelength followed by nearly immediate re-radiation
usually at a different wavelength.
Fluorescent lights, CFLs (much
more efficient than incandescent,
80% energy used as heat)
Light energy is stored and then re-emitted slowly over a
long time.
Glow in the dark toys
Light produced by friction or crushing.
Wintogreen Lifesavers, duct tape
Light-emitting diode [LED]:
Electronics devices, new
Christmas lights
Transforming electrical energy directly into light energy;
small electric current can cause semiconductor materials to
emit light
Electric Discharge:
Electric current is passed through air or another gas
Lightning, neon signs, plasma ball
SNC2D – Physics: Light and Geometric Optics
Homework Questions:
1. Which kinds of light sources might be considered natural sources, and which of them might
be considered artificial?
Natural: bioluminescence, triboluminescence, phosphorescence, electric discharge (lightning)
Artificial: incandescence, electric discharge, LED
Both natural and artificial: fluorescence, chemiluminescence
2. What is the difference between fluorescence and phosphorescence?
Fluorescence: absorbs energy and immediately re-radiates light energy, while
phosphorescence re-radiates the energy as light over a long time
3. What might be the advantages and disadvantages of using incandescent, fluorescent or LED
lighting in one’s home?
Incandescent: inexpensive, but wastes most energy (95%) as heat and don’t last long, safetyhazard - burns
Fluorescent: more expensive than incandescent, more energy efficient, lasts longer, safety
hazard – mercury in bulbs
LED: most expensive, very energy efficient, light colours limited right now
4. Opinion: Is a plasma television or an LCD television better for the environment? (see pp.
398-399, Pearson) Consider factors such as typical size and weight of both kinds of
televisions, the amount of energy used to operate them, the environmental impact of the
materials/chemicals used in them (consider the manufacturing stage as well as what happens
at the end of the products’ lives).
LCD televisions: last longer, lighter, thinner, use less energy, but have both mercury and
nitrogen trifluoride (potent GHG)
Plasma: sharp and detailed displays, good for large displays, but uses much more energy
If more electricity is generated through renewable sources, perhaps the energy consumption of
plasma tvs will be less significant