Light/geometrical optics

Question 1

light

Answer 1

form of energy e.g. crooke’s radiometer, solar panels. travels in straight lines

Question 2

luminous

Answer 2

makes its own light e.g. sun

Question 3

non-luminous

Answer 3

does not make its own light, instead reflect light e.g. moon

Question 4

reflection

Answer 4

the bouncing of light off an object

Question 5

diffuse reflection

Answer 5

reflection of light in all directions off a rough surface

Question 6

laws of reflection

Answer 6

1. incident ray, reflected ray and normal at point of incidence all lie on the same plane
2. angle of incidence (i) = angle of reflection (r)

Question 7

regular reflection

Answer 7

reflection of light off a shiny, smooth surface so that angle of incidence = angle of reflection

Question 8

virtual image

Answer 8

image formed by the apparent intersection of light rays

Question 9

real image

Answer 9

image formed by the actual intersection of light rays

Question 10

parallax

Answer 10

the apparent movement of one object relative to another due to the motion of the observer

Question 11

lateral inversion

Answer 11

in a plane mirror the image is back to front

Question 12

concave mirror

Answer 12

converging mirror

Question 13

convex mirror

Answer 13

diverging mirror

Question 14

focal length formula

Answer 14

1/f = 1/u + 1/v

Question 15

magnification

Answer 15

m = v/u
m = image height/object height

Question 16

refraction

Answer 16

the bending of light when travelling from one medium to another

Question 17

light travelling from rarer to denser medium

Answer 17

refracted towards normal

Question 18

light travelling from denser to rarer

Answer 18

refracted away from normal

Question 19

laws of refraction

Answer 19

1. incident ray, refracted ray and normal all lie on same plane
2. ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant (snell’s law) i.e. sin i/ sin r = n

Question 20

snell’s law

Answer 20

Sin(i)/Sin(r) = n
n= refractive index when light travels from a vacuum into a medium

Question 21

refractive index retracing path

Answer 21

it can be said that for any two media x, y: xny = 1/ynx

Question 22

total internal reflection

Answer 22

when light going from a denser to a rarer medium strikes the second medium at an angle greater than the critical angle, all the light is reflected back into the denser medium

Question 23

critical angle

Answer 23

the angle of incidence when the angle of refraction is 90 deg. when light is travelling from a denser to a rarer medium

Question 24

snell’s window

Answer 24

since light can retrace its path it is found that if light is to enter the water from air and arrive at the point P below the surface, only light which strikes the water within a circle of radius r found above will reach P.
if you are underwater and looking up, light can only enter the water through the circle of radius r (snell’s window). product of TIR

Question 25

refractive index (depth)

Answer 25

n = real depth/ apparent depth

Question 26

refractive index (speed of light)

Answer 26

n = speed of light in air (c)/speed of light in medium (c2)

Question 27

uses of TIR

Answer 27

fibre optics, reflective roadsigns, bicycle safety reflector

Question 28

optical fibre

Answer 28

a very thin transparent solid rod through which light can travel by TIR
*know how to draw

Question 29

uses of optical fibres

Answer 29

1. telecommunications
2. endoscope
3. used with dentist drill to see inside mouth

Question 30

mirage

Answer 30

image of the sky seen on the ground. formed due to TIR when light passes through different layers of hot and cold air

Question 31

advantages of optical fibres

Answer 31

1. less energy cost than electrical cables
2. smaller than elec. cables to carry same amount of signals
3. interference less than in electrical cables

Question 32

convex lens

Answer 32

converging lens

Question 33

concave lens

Answer 33

diverging lens

Question 34

power of a lens

Answer 34

P = 1/f
P = P1 + P2
unit: m^-1

Question 35

power of accommodation of the eye

Answer 35

the ability of the eye to focus a real image on the retina by changing its focal length using the ciliary muscles

Question 36

least distance of distinct vision of the eye

Answer 36

smallest distance from which an object can be seen clearly by the eye without strain

Question 37

short sighted

Answer 37

person can see objects nearby clearly but cannot bring distant objects into focus
fixed with concave lens

Question 38

long sighted

Answer 38

person can see distant objects clearly but cannot bring nearby objects into focus
corrected with convex lens

Question 39

converging focusing system of the eye

Answer 39

cornea, lens, aqueous humour, vitrious humour

Question 40

image formation in retina

Answer 40

real and inverted, brain corrects image by making it upright