Optics Flashcards
1
Q
The sun is ________ from the earth.
A
1.5 x 10^8 km
2
Q
How is light produced?
A
Nuclear reactions within the sun produces lots of energy, expressed in the form of light.
3
Q
We need the sun to:
A
- Keep the surface of the earth warm
2. Carry out photosynthesis in land and water ecosystems
4
Q
Properties of Light
A
- Travels in straight lines
- Travels in a vacuum
- Transferred by radiation
- Doesn’t require a medium
- Has both electric and magnetic properties
5
Q
Medium
A
any physical substance through which energy can be transferred
Conduction (solids) and convection (liquids + gases) require a medium
6
Q
Photons
A
Tiny packets of light
7
Q
Wavelength
A
Distance from one crest or trough to another
8
Q
Electromagnetic Waves Properties
A
- Are not visible
- Travel through a vacuum
- Travel at the speed of light
9
Q
Electromagnetic spectrum def
A
Classification system based on the energy of waves
10
Q
Electromagnetic spectrum order + energy/wavelenth
A
Radiowaves, microwaves, infrared, visible, UV, x-ray, Gamma
Gets more energy and shorter wavelength
11
Q
Radiowaves
A
- Communication in mines, submarines, aircraft
- TV signals, radio, MRI
12
Q
Microwaves
A
- Microwaves
- Radar in cars, airplanes
- Satellites
13
Q
Infrared light
A
- Image infrared radiation
- Motion sensors, burglar alarms, night vision googles
- Remote control
14
Q
Visible light
A
Photosynthesis
15
Q
Ultraviolet light
A
- Disinfect water
- DNA analysis
- Reveal substances unseen in visible light
16
Q
X-Rays
A
- Medical imaging
- Security in airports
- Photographing in machines to check for damage
17
Q
Gamma Rays
A
- Sterilize medical equipment
- Cancer treatment
18
Q
Visible Light
A
- Any electromagnetic wave that human eye can detect
- Consists of 7 different colours
- Red has longest wavelength (700 nanometers)
- Violet has the shortest wavelength (400 nanometers)
- Red Orange Yellow Green Blue Indigo Violet (ROY G BIV)
19
Q
How Do Objects Produce Light?
A
- Atoms within the object absorb energy
- Atoms are now in an excited state
- Atoms quickly release energy
- Energy sometime released in the form of light
20
Q
Incandesence: how?
A
- Light produces when objects are heated to very high temperatures
- Incandescent light bulbs are only 5-10% efficient at producing light, the rest is lost as heat
21
Q
Incandesence: examples
A
- Incandesence bulb
- Burning candle
- Stove element
22
Q
Electric Discharge: how?
A
- Electricity is passed through gas
- The electricity allows electrons to absorb energy and release it as photons of light
23
Q
Electric Discharge: examples
A
- Neon lights
- Lightning bolts
24
Q
Phosphoresence: how?
A
Occurs when an object absorbs UV light and returns it for several seconds to days causing them to glow for longer
25
Phosphoresence: examples
- Glow in the dark
| - Dials on wristwatches or clocks
26
Fluorescence: how?
- Occurs when object absorbs UV light and immediately releases a lower energy light in visible range
- Can provide same light output as an equivalent incandescent bulb but produces less heat and less electricity
27
Fluorescence: examples
- Fluorescent light bulbls
| - Highlighters
28
Chemiluminscence: how?
Light is generated by the energy released in a chemical reaction
29
Chemiluminscence: examples
Glow sticks
30
Biolominescence: how?
Light is produced by chemical reactions in living organisms with litttle or no heat produced
31
Biolominescence: examples
- Marine organisms (jellyfish)
| - Fireflies
32
Triboluminescence: how
The production of light when crystals are scratched, crushed, or rubbed
33
Triboluminescence: examples
Quartz crystals
34
Ray Model of Light
- Show the path of light
- Light ray= straight line with arrow
- Ray box or flashlight illustrates that light travels in straight lines (you never see a beam of light coming out of a flashlight crooked)
- When rays come from a point source (candle), they radiate out in diff directions
35
Specular reflection
series of parallel incident rays strikes a mirror, reflected rays are parallel to each other
36
Diffuse reflection
When parallel rays strike an irregular surface, the reflected rays are scattered = doesn’t produce a clear image
37
Transparent objects
- materials that absorb and reflect little to no light
- allows light to pass it easily
- allows objects behind it to be clearly seen
38
Translucent object
- materials that absorb and reflect some light
- most of light passes through with some change in direction
- does not allow you to clearly see objects behind it
39
Opaque objects
- objects that do not let light pass through
all incident light is either absorbed or reflected
- cannot see objects behind opaque materials
40
Laws of Reflection
1. Angle of incidence equals the angle of reflection in a plane mirror
2. The incident ray, reflected ray, and the normal all lie on the same plane (2 dimensional surface)
41
Rules to remember when drawing diagrams:
- Label degrees of angles
- Number rays
- Anything behind the mirror is dashed
- The normal is dashed
- Rays have to have arrows
42
Index of Refraction def
Ratio of speed of light in a vacuum and the speed of light in that medium
43
Calculate index of refraction formulas
```
n = c/v
n = sin
```
44
Concave def
Converging; inner surface is reflective
45
Convex def
Diverging; outer surface is reflective
46
Concave: SALT beyond C
Smaller
Inverted
Between C and F
Real
47
Concave: At C
Same size
Inverted
At C
Real
48
Concave: Between C and F
Larger
Inverted
Beyond C
Real
49
Concave: At F
NO CLEAR IMAGE
50
Concave: Inside F
Larger
Upright
Behind mirror
Virtual
51
Concave Rules
- any incident ray parallel to the principle axis will reflect to pass through F
- an incident ray that passes through C will reflect back onto itself
- an incident ray that passes through F will reflect off the mirror parallel to the principle axis
- a light ray at V will follow the law of reflection with the principle axis being the normal
52
Convex SALT
Smaller
Upright
Behind mirror
Virtual
53
Refraction
Bending of light when it passes from one medium to another in which speed and direction of light changes
54
Refraction: rare to dense
towards normal
55
Refraction: dense to rare
away from normal
56
Total internal refraction conditions
1. Light is travelling more slowly in the first medium than in the second
2. The angle of incidence is large enough that no refraction occurs in the second medium. Instead the ray is reflected back into the first medium
57
Refraction: angle of incidence is smaller than critical angle
both the refraction and reflection occur at the boundary between the 2 media
58
Refraction: angle of incidence is the critical angle
refracted ray lies along interface
59
Refraction: angle of incidence larger than critical angle
All light is reflected back into first medium; total internal reflection, no refraction.
60
n
index of refraction (is specific for a particular substance)
61
c
speed of light in a vacuum/air (3.00 x 10^8 m/s)
62
v
speed of light in a given medium
63
Sun - how is light produced
H atoms collide and combine to form Helium, releasing energy; some in the form of light.
63
Light Emitting Diode: examples
- christmas lights
- traffic lights
- illuminated signs
65
Light emitting diode: how?
- electricity is run through semiconductor and can only move 1 direction
- certain semiconductors will produce visible light
- don't require filament and produce less heat and waste
66
Concave: application
- search light: light source is at focus and reflected rays form parallel beam
- telescope: parallel light rays focused into clear image after reflecting off concave
67
Convex: application
- reflected rays from object never form real image
- brain projects rays behind mirror = smaller, upright, virtual image
- show wide range in cameras or car side-view mirrors
