Unit 2: Lesson 9 - Refraction of light

Refraction - ?

Refraction - the bending of light as it

travels, at an angle, from a material with one

refractive index to a material with a different

refractive index

Sun dogs, or mock suns, are technically called?

appear as? formed when?

Sundogs are formed by?

- Sun dogs, or mock suns, are technically called solar parhelia (parhelia meaning "with the sun") and

- appear as bright bursts of light

- formed when sunlight

- passes through ice crystals at the proper angle.

Sundogs are formed by plate shaped hexagonal ice crystals in high and cold cirrus clouds

This optical effect is due to refraction.

As light passes from one transparent

medium to another, it changes speed, and

bends.

How much this happens

depends on the refractive

index of the mediums and

the angle of incidence.

This optical effect is due to refraction.

As light passes from one transparent

medium to another, it changes speed, and

bends.

How much this happens

depends on the refractive

index of the mediums and

the angle of incidence.

Fermat's Principle?

Fermat's Principle

- When light travels from one

point to another, it follows the path that will take the least time.

Refraction and Rays

- refracted ray?

- angle of refraction (R)?

Refraction and Rays

- refracted ray = the ray that is bent upon entering a second medium

- angle of refraction (R) = the angle between the normal and a refracted ray

Direction of the Refracted

Ray

- when a light ray travels from a medium in which its speed

is faster (air) to a medium in which its speed is slower

(water) the refracted ray does what?

- Medium 2: more dense 🡪 light moves ?

-Light Ray: bends how and to where?

Direction of the Refracted

Ray

- when a light ray travels from a medium in which its speed is faster (air) to a medium in which its speed is slower (water) the refracted ray bends toward the normal

- Medium 2: more dense 🡪 light moves slower

- Light Ray: bends towards the normal

Direction of the Refracted

Ray

- when a light ray travels from a medium in which its speed

is slower to a medium in which its speed is faster, the

refracted ray does what?

- Medium 2: less dense 🡪 light moves ?

- Light Ray: bends how and to where ?

Direction of the Refracted

Ray

- when a light ray travels from a medium in which its speed is slower to a medium in which its speed is faster, the refracted ray bends away from the normal

- Medium 2: less dense 🡪 light moves faster

- Light Ray: bends away from the normal

Summary: Direction of Refraction

FAST to SLOW

- light ray does what?

- Example: ?

SLOW to FAST

- light ray does what?

- Example: ?

Summary: Direction of Refraction

FAST to SLOW

- towards the normal

- Example: Air to Water

SLOW to FAST

- away from the normal

- Example: Water to Air

The Bent Straw

- Why does the straw appear in two pieces at the waters' surface?

The Bent Straw

- Light coming from the part of the straw

below the surface of the water is traveling

from water (more dense) to air (less dense)

- The speed of light is faster in air than in

water, so light will bend away from the

normal

- The human brain perceives light to

travel in straight lines, so a virtual

image of the lower part of the straw is

formed, making the straw appear bent

(optical illusion)

Dispersion - the process of ?

- white light (all wavelengths of visible light) refract how many time? when?

Dispersion

- the process of separating colours by refraction

white light (all wavelengths of visible light) refract twice:

1. when it enters the prism

2. when it leaves the prism (separates into a spectrum of

colours)

Dispersion

- each colour of light travels at what speed?

- only in a what does what happen to colours?

- e.g.

Dispersion

- each colour of light travels at a slightly different

speed

- only in a vacuum (space with no matter) do all

colours travel at the same speed: 3.00 x 108 m/s

- e.g. blue light bends more than red light (blue light

travels slower than red light)

How much of the light

refracts?

- speed of light in a vacuum is?

- the speed of light in any other medium is?

How much of the light

refracts?

- speed of light in a vacuum is

- the speed of light in any other medium is less

than that

e.g. the speed of light in water is

2.26 x 108 m/s

- Index of Refraction - ?

- the index of refraction is always ?

- as the speed of light ____ due to the medium, the index of refraction ________

Index of Refraction

- the ratio of the speed of light in a vacuum to the

speed of light in a given medium

- the index of refraction is always greater than 1

- as the speed of light decreases due to the medium, the index of refraction increases

Formula Manipulation

n = ?

c = ?

v = ?

C = formula?

n = formula?

V = formula?

Formula Manipulation

n = index of refraction

c = speed of light in a vacuum

v = speed of light in a medium

C = n x V

n = C/V

V = C/n

practice

practice