science- 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

Everyday items

Environmental

What is light and how is it produced?

A visible form of energy
Has properties of and behaves like a wave
Is a form of electromagnetic radiation (vibrations of electrical and magnetic fields through space)

produced when excited electrons at a higher energy orbital return to their stable ground state (lower energy)
emit the energy difference as a visible wave (different energies = different colours)
Sources of Light (pp. 470-476, Science Perspectives 10, Nelson)
Source of Light
Example
Incandescence:
Incandescent light bulb (very inefficient, ~95% energy used as
Light emitted from a hot body (a heated filament) due to its heat) temperature.
Bioluminescence: (Greek "bios" for "living" and the Latin
"lumen" for "light")
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.
Chemiluminescence:
Glowsticks, "Glo" necklace
Light produced from a chemical reaction without a rise in temperature
Fluorescence:
Fluorescent lights, CFLs (much more efficient than incandescent, 80% energy used as heat)
Light produced by the absorption of radiation at one wavelength followed by nearly immediate re-radiation usually at a different wavelength.
Phosphorescence:
Light energy is stored and then re-emitted slowly over a long time.
Glow in the dark toys
Triboluminescence:
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
Sources of Light Homework Questions:
1. Which kinds of light sources might be considered natural sources, and which of them might be considered artificial? (Be careful! Light sources can be both.)
Natural Sources
Artificial Sources
Electric discharge (e.g. lightning),
LEDs, chemiluminescence, electric discharge
bioluminescence (fireflies), incandescence (neon signs), incandescence (Edison bulbs),
(sun)
fluorescence (light bulbs)
2. How are fluorescence and phosphorescence similar? How are they different?
Similarities)
Differences)
Involve absorbing energy and then re-
Fluorescence emits light immediately,
emitting the energy as light
phosphorescence over a long period of time;
Fluorescence emits light only as long as energy is being provided (e.g. electricity)
3. Using the information on the back page as well as your own knowledge, fill out the following chart of advantages and disadvantages of using incandescent, fluorescent or LED lighting in one's home.
Incandescent
Advantages, Benefits Cheapest bulb cost
Disadvantages, Costs
Most of energy is wasted as heat, highest energy cost;
Fluorescent (CFL)
Not as expensive as LED, more
Contains mercury vapour -
energy efficient than incandescent requires special disposal; colour?
LED
Most energy efficient, longest life, lowest cost (including energy) over life of the bulb
Higher initial cost of replacing bulb;
Based on monetary cost, energy usage, and environmental and aesthetic considerations, what would be your choice of lighting at home?
If you are able to pay the higher initial costs of LED bulbs, LED bulbs will last the longest and cost the least in energy costs, as well as waste the least electrical energy.
Electromagnetic Waves in our Society
(p. 466, Science Perspectives 10, Nelson)
Light that is visible to human eyes make up only a very small part of all the electromagnetic waves that travel through space and our world at any moment.
Electromagnetic waves are waves that are created as a result of vibrations between an electric field and a magnetic field. Unlike water waves, they do not require a medium (material), and can therefore travel through space.
Electromagnetic waves (including light) travel very fast: 300 000 000 metres per second in a vacuum!
- Increasing energy
MN
0.0001 nm 0.01 nm
Gamma rays
Xrays
Increasing wavelength
10 nm
1000 nm 0.01 m
Ultraviolet
Infrared
1 cm
1 m
Radio waves
Radar TV FM
100 m
AM
Visible light
400 mm
Violet
Type of electromagnetic wave
Radio
Infrared (IR, heat)
Visible
Ultraviolet (UV)
X-rays and gamma rays
500 nm
600 nm
Use/phenomena
AM/FM radio, tv signals, cellphones, radar, astronomy
Remote controls, heat detection, physical therapy (heating)
Range of human vision
Causes skin to tan/burn, increases skin cancer risk, kills bacteria (sterilization)
Medical imaging, cancer treatment, security equipment
700 nm
Red
Wavelength Range
> 1 cm long
700 nm - 0.05 cm
400 - 700 nm
10 - 400 nm
< 10 nm
In optics, we often deal with numbers that are very small (e.g. the wavelength of gamma rays is less than 0.01 nm = 0.000 000 000 001 m = 1.0 × 10-" m) or very large (the speed of light in a vacuum is 300 000 000 m/s = 3.0 ×10° m/s), so we often need to use scientific notation and to do unit conversions.
SNC2D - Propagation of Light
Light bulb
hole in cardboard
paper screen
bright spot
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1. Prediction: before group discussion - do this individually!
Predict how the bright spot position on the screen will change if the screen and cardboard are held still and the light bulb is moved in the following directions: (show by sketching the position on the screen)
A. Light moved
Fa
notes: after discussion or testing
Light moves up, bright spot
moves down
B. Light moved down
Light moves down, bright spot
moves up
C. Light moved left [label as LJ. Light moved right [Label as R]
Light moves left, bright spot moves right. Light moves right, bright spot moves left.
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1. Now share your diagrams with your seating partners. Change your diagrams if you are convinced they are in error. Show the changes on the diagrams above. Note why you made the changes.
2. Now test out your predictions. Show changes from your predictions and note any reasons why.
3. Summary: What characteristic of light accounts for where the position of the bright spot appears on the screen? Explain.
The Ray Model of Light - light travels in straight lines as rays
can help explain image formation for cameras, and behavior of light when it strikes a mirror or lens