Optics - Refraction Flashcards Preview

English > Optics - Refraction > Flashcards

Flashcards in Optics - Refraction Deck (42):
1

If the light travels from a "fast" medium to a "slow" medium it bends towards or away from the normal?

FST - towards

2

If the light travels from a "slow" medium to a "fast" medium it bends towards or away from the normal?

SFA - away

3

What is total internal reflection

When a wave from a slow medium to a fast medium enters at a degree larger than the incident angle, the wave can be trapped inside the slow medium

4

What is critical angle

When the angle of incidence results in the angle of refraction to be 90* to the normal (on the boundary line)

5

What are examples of refraction phenomenon?

Apparent depth: the illusion the object is closer then it appears because our brains can only trace back the reflected Rays - called the apparent depth
The mirage(flattened sun): you think you see something but it is just the displacement of light reflected off objects
Rainbows: each colour bends at a different speed and can only be seen when the sun is behind you

6

Examples of total internal reflection

1. Right angle prisms: 90*v- periscope, 180* - binoculars, bike reflectors
2. Diamonds: the critical angle for a diamond is 24* and light wave trying to escape must do so at a angle less then 24* and degree higher will totally internally reflect
3. Fibber optics: the light always hits the walls at an angle greater then the critical angle so it stays in the glass cylinder

7

Light does not reflect when it has an angle of:

0* it goes straight through

8

Rules for converging mirrors

1: a ray parallel to the PA will refract through PF
2: a ray through SF will refract parallel
3: a ray through the optic centre will continue unrefracted

9

Rules for diverging mirrors

1. a ray that us parallel to the PA will refract as I'd it came from PF
2: a ray that appears to go through sf will refract parallel to the PA
3 a ray that goes through the optic centre will continue unrefracted

10

What is a lens?

A thin transparent piece of glass with at ,east one curved side

11

What can lenses do

Can make images appear:
-smaller/larger
-inverted
-upside down
-misshapen

12

PF(F)

Principal focal point

13

SF(F')

Secondary focal point

14

2F

Twice the length of the focal point

15

F

Focal length: for the lens to the focal point

16

PA

Principal Axis

17

O

Optical centre (lens centre)

18

Use for converging lenses

Magnifying glass: put an object between SF and the lens to get a larger upright virtual image
Spotlight: put the beam at SF to produce a beam of parallel Rays
Projector: put object between SF and 2F the image will be larger, real and upside down. ~film must be loaded upside down
The camera: put the object beyond 2F of lens and a small inverted real image forms on the film or sensor
-farsightedness

19

Use for diverging lenses

Peepholes: as you look through the hole a smaller virtual image of the room are displayed in the lens
-nearsighted

20

Do

Distance from the object to the optical centre

21

Do

Distance of the image from the optical centre

22

Ho

Height of the object

23

Hi

Height of the image

24

F

Focal length of the lens; distance of the optical centre to the PF

25

Thin lens equation conventions

- the Do is always positive
-di are pos for real images and neg for virtual
-f is Pos for converging lenses and neg for diverging lenses

26

When the lens is converging the object is on the _____ side

SF

27

When the lens is diverging the object is on the _____ side

PF

28

Looking at a near object the ciliary muscles

Contract and make the lens short and fat

29

Looking at far objects the ciliary muscles

Relax and make the lens long and thin

30

Cornea

Light from an object enters the eye through the cornea. It does almost all of the light bending

31

Pupil

The light goes through the pupil which is a small opening

32

Iris

The iris is the coloured part of the eye that opens and closes to control the amount of light

33

Lens

The light then enters the lens and is bent slightly. The lens can change shape to bend he light rays more or less to produce a clear image

34

The ciliary muscles

The ciliary muscles are responsible for changing the shape of the lens

35

Rentina

The retina is on the back wall of the eye. The light energy is converted to electrical impulses by the photosensitive cells of the retina

36

Optic nerve

The optic nerve connects the eye to the brain. The brain takes the small inverted image and creates a flipped upright image

37

Red eye in flash photography

-light reflects off retinas
- purpose of double flash: flash causes pupils to contact so less light reflects off the retina
- no double flash > turn on more light so make pupils smaller

38

The human eye accommodation

The lens of the eye can change shape. This allows you to see things that are near and also to see things far away

39

Nearsightedness

You can see close but not far away. The lens bends the light too much and the image forms before the retina. A divergent lens corrects this problem by spreading the light rays out before they enter the eye

40

Farsightedness

You can see far but not close. Lens bends light too little and the image is formed behind the retina. A converging lens can fix this problem by focusing the Rays before they enter the eye.

41

Define refraction

Reflection is when a light wave travels from one medium into a different one at an angle, and the light bends.

42

Magnification

Has no units
If it is larger than 1 the image is larger than the object
If it is smaller than 1 the image is smaller then the object
It is pos for upright image and neg for an inverted image