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Flashcards in Light Deck (64):
1

where does light originate from?

the accelerated motion of electrons

2

how do you generate waves of electric and magnetic fields (electromagnetic waves)
And why?

when you shake a electrically charged rod back and forth in empty space
- because the moving charge is an electric current and it is surrounded by a magnetic field

3

the electric and magnetic fields of an electromagnetic waves are ____ to each other
and are what type of wave?

perpendicular
transverse wave

4

There is how many speeds for which the electric and magnetic fields remain in perfect balance, reinforcing each other as they carry energy through space

one speed

5

an electromagnetic wave travelling through space ______ (what about speed) and what is it due to?

it never changes speed
due to the law of conservation of energy

6

If light were to slow down what would happen

its changing electric field would create a weaker magnetic field which creates a weaker electric field and energy would be lost

7

if light were to speed up what would happen

its changing electric field would create a stronger magnetic field which creates a stronger electric field and energy would be increasing

8

Maxwell calculated the value of the speed of light to be what?

300 000 km/s

9

Maxwell discovered that light is simply what type of radiation between what frequency ranges

electromagnetic radiation
4.3 X 10^14 to 7 X 10 ^ 14

10

Maxwell proved that light of any kind is...

energy - carrying waves of electric and magnetic fields that continually regenerate each other and travel at single fixed speed

11

The classification of electromagnetic wavees acccording to frequency is the

electromagnetic spectrum

12

List the electromagnetic spectrum from longest to shortest wavelength

radio waves, mircrowaves, infrared light, visable light, ultraviolet light, xrays, gamma rays

13

List the electromagnetic spectrum from highest frequency

gamma rays, xrays, ultraviolet light, visable light, infrared light, microwaves, radio waves

14

the ___ the frequency of the vibrating charge, the _____ the wavelength of radiation

higher
shorter

15

visable light makes up less than a ______ of the measured electromagnetic spectrum

a millionth of 1%

16

what is the lowest frequency light that we can see with our eyes (colour)

red

17

the highest frequencies of visable light are nearly twice the frequency of red and appear

violet

18

what type of boundries are there between the regions

not sharp, they overlap

19

when a light wave with a single frequency strikes an object what 3 things can happen

- reflected by the object
- transmitted by the object
- absorbed by the object in which case its energy is converted to heat

20

The way a material responds depends on

the frequency of the light and the natural frequency of the electrons in the reieving material

21

Absorbtion occours when

the frequencies of the light waves is the same as the natural frequencies of vibration of the objects. these electrons will absorb the energy of the light wave

22

Reflection and transmission occour when

the frequencies of the light waves do not match the natural frequencies of vibration of the objects. the electrons vibrate for brief periods of time with small amplitutes; then the energy is transmitted as a light wave

23

If the object is transparent then..

the vibtrations of the elctrons are passed on to neighbouring atoms through the bulk of the material and reemitted on the opposite side of the object. such frequencies of the light waves are said to be transmitted

24

If the object is opaque...

the vibtrations of the elctrons are not passed on to neighbouring atoms through the bulk of the material. rather the electrons of the atoms on the material's surface vibrate for short periods of time and then reemit the energy as a reflected light wave. such frequencies of the light waves are said to be reflected

25

what is reflection

when light is returned into the medium from which it came

26

what is refraction

when light crosses from one transparent material into another

27

usually some form of what occurs when light interacts with matter

reflection,refraction,absorption

28

when there is nothing to obstruct its path light travels in

a straight line

29

What does the path of light always follow?

Fermat's Prinicple of Least Time

30

Fermat's Prinicple of Least Time

out of all possible paths that light might take to get from one point to another it takes the path that requires the shortest time

31

Following the principle of least time the least time path will be the

shortest path - if the speed doesnt change

32

The Law of Reflection states that

the angle of reflection is equal to the angle of incidence

33

When light is incident on a rough surface .....

it is reflected in many directions and is called a diffuse reflected

34

a flat mirror is called

a plane mirror

35

a virtual image is formed where and when

formed behind the mirror and is located at the position where the extended reflected rays converge

36

Image Characteristics
- Type
- Attitude
- Magnification
- Position

- real or virtual
- upright or inverted
- same size, smaller, larger
- distance from mirror surface

37

What are virtual images

image formed by rays that do not converge at the location of the image

38

what are real images

Image formed by rays that converge at the location of the image

39

When the mirror is curved, the sizes and distances of object and image are

no longer equal

40

Convex mirror

- curves outward
- virtual image formed is smaller and closer to the mirror than the object.

41

Concave Mirror

- curves inward
- virtual image is larger and farther away than the object

42

Does light travel at different speeds in different materials

yes

43

light travels how fast in a vacuum

300 000 km/s (c)

44

does light travel faster or slower speed in air

slightly slower speed

45

how fast does light travel in water comparative to vacuum

3/4ths

46

Index of refraction

how much the speed of light differs from its speed in a vacuum
- never less than one
- shown by the equation
n = speed of light in a vauccum (c)
---------------------------------------------
speed of light in a material
n = c/v

47

Whether reflection or refraction, the path of light follows

fermat's principle of least time

48

When does refraction occour

when the average speed of light changes in going from one medium to another.

49

when light travels from less dense to more dense medium it

slows and bends towards the normal

50

when light travels from more dense to less dense medium it

speeds up and bends away the normal

51

if the angle is large enough then the angle of
refraction will be

parallel to the medium boundry

52

what is the critical angle

the minimum angle of incidence at which a light ray is totally reflected

53

If the incident angle is greater than the critical angle what happens and what is it called?

all light is reflected
Total Internal reflection

54

What is total internal reflection

If the incident angle is greater than the critical angle and all light is reflected
critical angle - angle of incidence when angle of reflection = 90

55

Snell's law

- quantitative law of refraction

56

diverging lens

thinner in the middle

57

converging lens

thicker in the middle
roundish

58

when is an image real?

when the light rays actually converge and pass through the image
- real image can be seen on a piece of paper or a screen

59

when does a virtual image happen?

when the image is formed in locations where the light noes not converge
- always located behind the mirror

60

concave mirror

converging
curves in (backwards c)

61

convex mirror

diverging
curves outwards (c)

62

concave lens

diverging
thinner in middle

63

convex lens

converging
roundish - fat in middle

64

if it is converging and the object is at the focal point what happens

no image