1
Q
Luminous objects
A
Produce their own light
2
Q
Examples of luminous objects
A
Sun, light bulb, match, flashlight
3
Q
Non-luminous objects
A
Do not produce their own light and can only be seen by reflecting light
4
Q
Examples of non-luminous objects
A
Textbook, pencil, bicycle
5
Q
Incandescence
A
The production of light as a result of high temperature
6
Q
Examples of incandescence
A
The filament of a stove burner glowing when its on, a burning candle
7
Q
How does an incandescent light bulb work?
A
The electricity going through a thin wire filament makes it become so hot that it gives off visible light and emits infrared light
8
Q
Why is an incandescent light bulb inefficient?
A
Only 5-10% of the energy going through the incandescent light bulb becomes visible light, with the rest being converted to heat
9
Q
Electric discharge
A
The production of light by passing an electric current through a gas
10
Q
Phosphorescence
A
A special material that absorbs ultraviolet light and emits visible light over an extended period of time (from seconds to days)
11
Q
Flourescence
A
A special material that absorbs ultraviolet light and immediately emits visible light
12
Q
Example of flourescence
A
Fluorescent light tubes are light tubes in which electricity makes a mercury vapour inside emit ultraviolet light, which htis the fluorescent material on the inner surface, emitting visible light as a result
13
Q
Efficiency of compact fluorescent lights compared to incandescent light bulbs
A
- CFLs are 4-5x more energy efficient than incadescent light bulbs
- Produce the same amount of light while using less electricity and producing less heat
- Incandescent light bulbs cost less to buy but are more expensive to operate; CFLs are more costly initially but are cheaper to run and last much longer
- CFLs contain mercury and thus should be recycled properly rather than alongside normal household waste
14
Q
Chemiluminescence
A
The production of light as the result of a chemical reaction with little or no heat produced
15
Q
Example of chemiluminescence
A
Glow sticks - have one chemical in a small, narrow glass vial in the middle of the stick and another in the main body. Bending the light stick in the middle causes the small glass vial to break, allowing the two chemicals to mix in the main body of the stick. The chemical reaction that occurs produces visible light.
16
Q
Bioluminescence
A
The production of light in living organisms as the result of a chemical reaction with little or no heat produced
17
Q
Examples of animals that have bioluminescence
A
Bacteria, fungi, marine invertebrates, fish, glow-worms, fireflies
18
Q
What do scientists believe the purpose of bioluminescence is?
A
- Protection from predators
- To kill prey
- To attract mates
19
Q
Triboluminescence
A
The production of light from scratching, crashing, or rubbing certain crystals
20
Q
Light-emitting diode (LED)
A
The production of light through electric current flowing in semiconductors
21
Q
Semiconductor
A
A material that allows an electrical current to flow in only one direction
22
Q
Examples of LEDs
A
Christmas lights, illuminated signs, traffic lights
23
Q
Efficiency of LEDs
A
- Do not require filament
- Produce less heat as byproduct
- More energy efficient compared to incandescent lights
24
Q
How does the Sun produce its energy?
A
Through nuclear reactions occurring within the sun
25
Properties of light
1. Light travels at a high speed
2. Light travels in straight lines
26
What is light, according to quantum theory?
Discrete packets of energy called photons
27
Medium
Any physical substance that acts as a carrier for energy to travel (air, oil, water, etc)
28
How does light travel?
Through waves called radiation - NOT through a medium
29
Radio wave applications
AM/FM radio, TV signals, cellphone communications, radar, and astronomy (discovery of pulsars, which emit radio waves)
30
Microwave applications
Telecommunications, microwave ovens, astronomy (background radiation associated with the Big Bang)
31
Infrared light applications
Remote controls, lasers, heat detection, remote sensing, keeping food warm, astronomy (discovering the chemical composition of celestial bodies), physical therapy
32
Visible light applications
Human vision, theatre/concert lighting, rainbows, visible lasers, astronomy (optical telescopes)
33
Ultraviolet light applications
Tanning/sunburns, increasing risk of skin cancer, stimulating production of vitamin D, killing bacteria in food and water, "black" lights, ultraviolet lasers, astronomy (discovering the chemical composition of celestial bodies)
34
X-ray applications
Medical imaging (such as of teeth or broken bones), security equipment, cancer treatment, astronomy (study of binary star systems, black holes, centres of galaxies)
35
Electromagnetic spectrum
Radio waves > microwavese > infrared light > visible light > ultraviolet light > X-rays > gamma rays
36
Visible spectrum from fastest to slowest
Red > orange > yellow > green > blue > indigo > violet
37
Relationship between wavelength and frequency in electromagnetic waves
Indirect relationship
- As one characteristic increases, the other decreases
- ie; as wavelength increases, frequency decreases
38
Wavelength and frequency relationship
Short wavelengths have a high frequency, long wavelengths have a low frequency
39
Electromagnetic wave frequency & energy relationship
High frequency waves have high energy, low frequency waves have low energy
40
Options when light strikes matter and definition
1. Transmitted - the light passes through the substance
2. Reflected - the light bounces off an object
3. Absorbed - the light is absorbed by an object and is converted to heat
41
Classifications of matter
1. Transparent
2. Translucent
3. Opaque
42
Transparent
- Transmits all or almost all incident light
- Object(s) can be clearly seen through the material
- Ex. clear glass
43
Translucent
- Transmits some incident light
- Absorbs or reflects the rest
- Objects are not clearly seen through material
44
Opaque
- Does not transmit any incident light
- Objects are not seen through material
- All incident light is either absorbed or reflected
45
Plane mirrors
Flat, polished surface that reflects an image
46
Image
A reproduction of an original object created through the use of light
47
Reflection
The bouncing back of light from any surface
48
Incident ray
An incoming ray that strikes a surface
49
Reflected ray
A ray that bounces off a reflective surface
50
Normal
An imaginary line perpendicular to the surface
51
Angle of incidence
Angle between the incident ray and the normal
52
Angle of reflection
Angle between the reflected ray and the normal
53
Laws of reflection
1. The angle of incidence equals the angle of reflection
2. The incident ray, the reflected ray, and the normal all lie on the same plane
54
Specular reflection
The reflection of light off a smooth, shiny surface
- ex. the reflection off a plane mirror, the surface of very still water, a flat piece of aluminum foil
55
Diffuse reflection
The reflection of light off an irregular surface
- ex. the reflection off a water surface with waves, a crumpled piece of aluminum foil
56
Specular reflection rules
- Incident rays are parallel
- Reflected rays are parallel
- All angles of incidence and corresponding angles of reflection are equal
- A viewer would see approximately 100% of incident light
57
SALT
S stands for size, possible descriptions include smaller, same, or larger
A stands for attitude, possible descriptions include upright or inverted
L stands for location, descriptions are in relation to mirror
T stands for type, possible descriptions include real or virtual
58
SALT in plane mirrors
Size is same as object
Attitude is upright, laterally inverted
Location is behind the mirror
Type is virtual
59
Virtual images
- An image where the light doesn't arrive at or come from the image location
- There is no light source behind the mirror because it is opaque
- The light only appears to come from the image
- Your eyes detect light rays but your brain determines where the image is located
60
Concave mirrors
Mirrors where the reflecting surface curves inwards
61
Convex mirrors
Mirrors where their reflecting surfaces curve outwards
62
Centre of curvature
The centre of the sphere from which the mirror was sliced
63
Focal point
The point halfway between the surface of the mirror (vertex) and the centre of curvature
64
Focal length
The distance from the surface of the mirror to the focal point
65
Principal axis
The line that passes through the centre of the mirror, would represent the diameter of the circle
66
Concave mirror rules if the object is beyond C
S = smaller
A = inverted
L = between C & F
T = real image
67
Concave mirror rules if the object is at C
S = same size
A = inverted
L = at C
T = real image
68
Concave mirror rules if the object is between C & F
S = larger
A = inverted
L = beyond C
T = real image
69
Concave image rules if the object is at F
No image produced!
70
Concave image rules if the object is between F & V
S = larger
A = upright
L = behind mirror
T = virtual image
71
Convex mirror rules
S = smaller
A = upright
L = behind mirror
T = virtual
72
Car rearview mirrors - plane mirror application
- Useful because they always produce upright images
- Size is always the same as original objects (provides good perspective)
- Challenge in reversed images (emergency vehicles overcome this by writing their services backward in the front)
73
Stealth aircraft - plane mirror application
- Use plane "surfaces" to avoid detection via satellites emitting signals into the air
- Flat bottom and surfaces to reflect signals in the same angle they came (compared to rounded aircraft which spreads the signals in various directions)
- Have special paint and tape which absorbs wavelengths
74
Cosmetic mirror - concave mirror application
- Useful for applying makeup, shaving, because they can produce larger images
- Enlarged image can only be produced if the object (person) is standing between the focal point and vertex
75
Car headlights, flashlights, searchlights - concave mirror application
- Lightbulb is placed on the focal point and sends incident rates into the concave mirror through F
- Produces reflected rays parallel to principle axis
- Creates single, focused beam of light forwards
76
Solar ovens - concave mirror application
- All incident rays coming from the sun are parallel (due to its distance from the earth)
- Solar ovens capture these incident rays in a concave dish
- Incident rays are reflected through the focal point
- Oven is placed on the focal point so all the solar energy can heat up the food
77
Store security mirrors - convex mirror application
- Convex mirrors always produce upright images
- Images produced are smaller but provide wider view of store
- Similar use in stairwells and hospitals to see what is around the corner
78
Car passenger side mirrors - convex mirror application
- Wider view of road
- Image is always upright
- Produced image is smaller than original object so other cars are closer than they appear
79
What is refraction?
The bending of light as it passes from one medium to another
80
How does refraction occur?
When a light ray moves from one medium to another, its speed changes. This change of speed causes a refraction
- ie; the speed of a light ray in WATER is less than the speed of a light ray in air
81
Incident ray (in refraction)
The light ray travelling through the first medium toward the boundary
82
Refracted ray
The light ray travelling away from the boundary, through the second medium
83
Normal (in refraction)
Where the incident ray strikes the second medium and is perpendicular to the boundary between the two media
84
Angle of refraction
The angle between the refracted ray and the normal
85
Rules of refraction
WHEN THE SPEED OF LIGHT IN THE FIRST MEDIUM IS MORE THAN THE SPEED OF LIGHT IN THE SECOND MEDIUM:
- Light is bent towards normal
- Angle of refraction is smaller than the angle of incidence
WHEN THE SPEED OF LIGHT IN THE FIRST MEDIUM IS LESS THAN THE SPEED OF LIGHT IN THE SECOND MEDIUM:
- Light is bent away from the normal
- Angle of refraction is greater than the angle of incidence
86
Speed of light
In a vacuum, light travels at a speed of 3.00 x 10^8 m/s, but it travels at different speeds depending on the medium through which it is travelling.
87
Relationship between index of refraction and speed of light
- The larger the 'n' value (n = index of refraction), the slower light will travel in that media
- The smaller the 'n' value, the faster light will travel in that media
88
Critical angle
The angle of incidence at which the angle of refraction is equal to 90 degrees
89
Total internal reflection
- A phenomenon that involves the reflection of all light off the mediums boundary
90
Conditions that must be met for total internal reflection
1) Light is travelling more slowly in the first medium than in the second medium
2) The angle of incidence must be large enough to cause no refraction (must be greater than the critical angle)
91
Diamond cutter application to total internal reflection
- They cut the faces of diamonds so light entering the diamond undergoes total internal reflection
- Allows the light to bounce around as many times as possible in the diamond
- A well cut diamond will sparkle more than a poorly cut diamond
92
Misc. applications of total internal reflection
Optical fibres, endoscopes, laser beams in lucite rods
SNC2D - Grade 10 Academic Science
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