M4 Refraction

Question 1

Why does light refract

Answer 1

When light enters a more dense substance at an angle, the particles hit the substance at different times meaning it bends towards the normal and slows down

If it goes into a less dense substance it bends away from the normal and speeds up

Question 2

What is the first law of refraction

Answer 2

At the point where the light hits the substance, the incident ray, reflected ray and normal lie on the same plane

Question 3

In the equation n=c/v what do the letters stand for

Answer 3

n is refractive index
c is speed of light through a vacuum, 3 X 10^8
v is the speed of light through the material

Question 4

In the equation nsinθ=k

What do all the symbols mean

Answer 4

n is the refractive index
θ is the angle between the normal and incident ray
k is the constant

Question 5

What equation can you use when light travels from one medium to another

Answer 5

n1sin(θ1) = n2sin(θ2)

Question 6

If light enters a glass block from air at an angle of 30 degrees what is the angle of refraction

Refractive index of air is 1
Refractive index of glass is 1.5

Answer 6

1sin30 = 1.5sinθ

1/3 = sinθ
θ = 19.5 degrees

Question 7

what happens if the angle of incidence is smaller than the critical angle

Answer 7

the light ray is refracted

Question 8

what happens if the angle of incidence equals the critical angle

Answer 8

the light ray is refracted along the boundary

Question 9

what happens if the angle of incidence is greater than the critical angle

Answer 9

the light ray is NOT refracted and total internal reflection occurs

Question 10

what is TIR

Answer 10

total internal reflection
occurs at the boundary between 2 different media
when light strikes the boundary at a larger angle than the critical angle
all light is reflected back into the original medium and no light is refracted out of the original medium

Question 11

what are the conditions for TIR

Answer 11

angle of incidence needs to be larger than the critical angle
rays must travel from a more dense to a less dense medium

Question 12

what does the equation sinc = 1/n mean

Answer 12

to calculate the critical angle for material to air boundary

sin of the critical angle = 1 / refractive index

Question 13

why do we use a semi-circular block rather than a rectangular block in the experiment to determine the critical angle

Answer 13

so incident ray enters at 0 degrees

so refraction occurs inside the block

Question 14

draw a diagram of TIR happening inside a prism

Answer 14

look it up

Question 15

in refraction what happens if

a) the angle of incidence is smaller than the critical angle?
b) the angle of incidence equals the critical angle?
c) the angle of incidence is bigger than the critical angle?

Answer 15

a) the ray is refracted and partially reflected
b) the ray is refracted along the boundary and partially reflected
c) total internal reflection