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Flashcards in Optics Deck (67):
1

The sun is ________ from the earth.

1.5 x 10^8 km

2

How is light produced?

Nuclear reactions within the sun produces lots of energy, expressed in the form of light.

3

We need the sun to:

1. Keep the surface of the earth warm
2. Carry out photosynthesis in land and water ecosystems

4

Properties of Light

- Travels in straight lines
- Travels in a vacuum
- Transferred by radiation
- Doesn’t require a medium
- Has both electric and magnetic properties

5

Medium

any physical substance through which energy can be transferred
Conduction (solids) and convection (liquids + gases) require a medium

6

Photons

Tiny packets of light

7

Wavelength

Distance from one crest or trough to another

8

Electromagnetic Waves Properties

- Are not visible
- Travel through a vacuum
- Travel at the speed of light

9

Electromagnetic spectrum def

Classification system based on the energy of waves

10

Electromagnetic spectrum order + energy/wavelenth

Radiowaves, microwaves, infrared, visible, UV, x-ray, Gamma

Gets more energy and shorter wavelength

11

Radiowaves

- Communication in mines, submarines, aircraft
- TV signals, radio, MRI

12

Microwaves

- Microwaves
- Radar in cars, airplanes
- Satellites

13

Infrared light

- Image infrared radiation
- Motion sensors, burglar alarms, night vision googles
- Remote control

14

Visible light

Photosynthesis

15

Ultraviolet light

- Disinfect water
- DNA analysis
- Reveal substances unseen in visible light

16

X-Rays

- Medical imaging
- Security in airports
- Photographing in machines to check for damage

17

Gamma Rays

- Sterilize medical equipment
- Cancer treatment

18

Visible Light

- 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

How Do Objects Produce Light?

1. Atoms within the object absorb energy
2. Atoms are now in an excited state
3. Atoms quickly release energy
4. Energy sometime released in the form of light

20

Incandesence: how?

- 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

Incandesence: examples

- Incandesence bulb
- Burning candle
- Stove element

22

Electric Discharge: how?

- Electricity is passed through gas
- The electricity allows electrons to absorb energy and release it as photons of light

23

Electric Discharge: examples

- Neon lights
- Lightning bolts

24

Phosphoresence: how?

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