Light

Question 1

Diffuse reflection

Answer 1

incident beam from parallel light reflects (scatters) in all directions

Question 2

example of diffuse reflection

Answer 2

light from paper you read from

Question 3

regular reflection

Answer 3

incident beam from parallel light is reflected as a beam of parallel light

Question 4

example of regular reflection

Answer 4

light reflected from a highly polished surface

Question 5

why does the glass in a household mirror complicate things?

Answer 5

because the light bends as it enters and exits

Question 6

Law 1 of reflection

Answer 6

the incident ray, the reflected ray and the normal all lie in the same plane

Question 7

Law 2 of reflection

Answer 7

the angle of incidence equals the angle of reflection

i=r

Question 8

normal

Answer 8

an imaginary line perpendicular to the mirror

Question 9

where are angles of incidence and reflection measured from?

Answer 9

the normal

Question 10

glancing angle

Answer 10

between the mirrors and the beam of light

Question 11

if you rotate a plane mirror by angle a, what happens to the reflected ray?

Answer 11

the reflected ray is deflected by an angle 2a

Question 12

whats special about the image in a plane mirror?

Answer 12

u=v

Question 13

u

Answer 13

distance from object to mirror

Question 14

v

Answer 14

distance from mirror to image

Question 15

type of image in a plane mirror 2

Answer 15

virtual

laterally inverted

Question 16

what is a virtual image

Answer 16

rays of light do not pass through a virtual image they just appear to do so

Question 17

a person 2m tall needs to see all of himself in the mirror, what length does it have to be? where should he place it?

Answer 17

1m, half way from the ground to the height of his eyes

Question 18

p

Answer 18

pole

Question 19

explain p

Answer 19

the centre of the mirror itself

Question 20

c

Answer 20

centre of curvature

Question 21

explain c

Answer 21

the centre of the sphere from which the mirror was cut

Question 22

f

Answer 22

focal point

Question 23

explain f

Answer 23

half way between c and p

Question 24

focal length

Answer 24

distance between p and f

Question 25

straight line that joins p f and c

Answer 25

principal axis

Question 26

m

Answer 26

magnification

Question 27

m = (2)

Answer 27

v/u = image distance/ object distance

Question 28

1/f =

Answer 28

1/u + 1/v

Question 29

real image v

Answer 29

posituev

Question 30

virtual image v

Answer 30

negative

Question 31

concave mirror f

Answer 31

positive

Question 32

convex mirror f

Answer 32

negative

Question 33

nature of image, when object at infinity (very far away)

Answer 33

formed on focal point, real image

Question 34

nature of image, when object a little outside c

Answer 34

image between c and f | real inverted diminished

Question 35

nature of image, when object at c

Answer 35

real, inverted and diminished, image at c

Question 36

nature of image, when object between c and f

Answer 36

image is real inverted and magnified

Question 37

nature of image, when object on f

Answer 37

image at infintiy. real, inverted, greatly magnified

Question 38

nature of image, when object inside f

Answer 38

located behind the mirror, virtual erect and magnified

Question 39

nature of image, when object anywhere in convex mirror

Answer 39

image behind the mirror, inside f | virtual, erect and diminished

Question 40

an object is placed 16cm in from of a concave mirror and an inverted image is formed 24cm in front of mirror. object is 2cm in size. calculate the focal length of the mirror and the size of the object

Answer 40

``` u= 16cm f = 9.6cm ```

Question 41

an image formed in a concave mirror of focal length 12cm is 3 times the size of the object. calculate the positions of the object for this to happen

Answer 41

u=16cm or 8cm

Question 42

2 uses of concave mirror

Answer 42

shaving or makeup mirror to give enlarged image | dentists mirror for enlarged image of a tooth

Question 43

2 uses of a convex mirror

Answer 43

security mirror in a shop | rear view mirror of a car (image is smaller, more is seen)

Question 44

definition of refraction of light

Answer 44

the bending of light as it passes from one medium to another of a different refractive index

Question 45

Law 1 of refraction

Answer 45

the incident ray, the refracted ray and the normal all lie in the same plane

Question 46

Law 2 of refraction

Answer 46

Snell's law | The sin of the angle of incidence is proportional to the sine of the angle of refraction

Question 47

sin i/sin r =

Answer 47

n

Question 48

refractive index of glass refers to

Answer 48

the refractive index of air to glass

Question 49

directly proportional graph

Answer 49

straight line graph through the origin

Question 50

c1/c2 =

Answer 50

n

Question 51

c1

Answer 51

speed of light in medium 1

Question 52

c2

Answer 52

speed of light in medium 2

Question 53

speed of light in air

Answer 53

2.99 x 10 to the power of 8

Question 54

real depth/apparent depth =

Answer 54

n

Question 55

state of no parallax

Answer 55

coincides even when you move right and left

Question 56

why should you avoid small values in experiments

Answer 56

they lead to greater percentage error

Question 57

one thing to avoid in light experiments

Answer 57

avoid the error of parallax when measuring distances

Question 58

real dept vs apparent depth, y vs x axis

Answer 58

real depth y axis apparent dept x axis (slope is n = real over apparent)

Question 59

critical angle

Answer 59

the angle in the more dense medium when the angle of refraction in the less dense medium is 90 degrees

Question 60

1/sinC=?

Answer 60

w n a

Question 61

outside layer of optical fibre called

Answer 61

cladding

Question 62

where does total internal reflection happen in an optical fibre?

Answer 62

at the boundary between the fibre and the cladding

Question 63

lense dense material in optical fibre

Answer 63

cladding

Question 64

how long will total internal reflection happen for in the fibre

Answer 64

ntil the light exits from the far end of the fibre

Question 65

2 uses of total internal reflection

Answer 65

in the telecommunications industry | in medical endoscopes

Question 66

3 reasons why it is better to use optical fibres instead of copper wire in the telecommunications industry

Answer 66

cheaper non-corrosive more information can be transmitted along the

Question 67

why wouldn't light bend in an experiment to show total internal reflection when passing through the glass the first time?

Answer 67

you shine it through on the normal

Question 68

dispersion of white light

Answer 68

the breaking up of a beam of light into its constituent colours which spread out to form a spectrum

Question 69

lamba 1 over lamba 2=

Answer 69

n

Question 70

when showing the recombination of a spectrum into white light, what should you label the angles as?

Answer 70

60 degrees

Question 71

what is the same/different about the 2 prisms to recombine a spectrum into white light

Answer 71

also equiangular near sides are parallel inverted though

Question 72

why does light reflect at 90 degrees in total with a normal looking right angled triangle at the end of it periscope

Answer 72

``` enters along normal, no bending angle of incidence is 45 degrees critical angle is 42 reflects back at 45 degrees add them up it looks like 90 degrees ```

Question 73

why is light reflected back along its own path when entering flat hypothenuse of right angled triangle bike reflectors

Answer 73

goes in through normal no bending at 45 degrees to side, total internal reflection at another 45 hits other side,at 45 and does the same thing 45 +45 = 90 plus another one = 180 degrees

Question 74

Concave mirror: light at infinity | 2

Answer 74

Image on f | Real

Question 75

Concave mirror: object outside c

Answer 75

Image real inverted and diminished

Question 76

Concave mirror: object on c

Answer 76

Image real inverted and same size

Question 77

*** Concave mirror: object between c and f

Answer 77

Image real, inverted and magnified

Question 78

Concave mirror: object on f

Answer 78

Image at infinity | Real and greatly magnified

Question 79

**** Concave mirror: object inside f

Answer 79

Image is virtual erect and magnified

Question 80

Convex mirror: anywhere in front of mirror

Answer 80

Image is virtual erect and diminished

Question 81

How do you get the focal length from a graph when given v and u values

Answer 81

Plot 1/u vs 1/v and f is 1/slope

Question 82

How do you find circle of light at the top of water when the bulb is underneath?

Answer 82

Use n=1/sinC to get C Using C find the radius of the circle pi r squared

Question 83

Converging lens: object between 2f and f

Answer 83

Real inverted and magnified

Question 84

Converging lens: object inside f

Answer 84

Image on the left of the lens | Virtual erect and magnified

Question 85

Diverging lens: object anywhere on the left side of the lens

Answer 85

Image on the left side of the lens | Virtual erect and diminished