Chapter 13

Question 1

converging lens

Answer 1

a lens that is thickest in the middle and that causes incident parallel rays to conserve through a single point after refraction

Question 2

diverging lens

Answer 2

a lens that is thinnest in the middle and that causes parallel light rays to spread apart after refraction

Question 3

how many refractions in a lens

Answer 3

1. air to glass
2. glass to air

Question 4

optical centre

Answer 4

point at the exact centre of the lens

Question 5

principal focus

Answer 5

the point on the principal axis of a lens where light rays parallel to the principal axis converge after refraction

Question 6

where are the principal focus for lenses

Answer 6

• converging: opposite side as rays
• diverging: same side as rays

Question 7

emergent ray

Answer 7

light ray that leave a lens after refraction

Question 8

imaging rules for converging lenses

Answer 8

1. a ray parallel to the principal axis is refracted through the principal focus
2. a ray through the secondary principal focus is refracted to the principal axis
3. a ray through the optical centre continues straight through without being refracted

Question 9

images in a converging lens

Answer 9

• beyond 2f: smaller, real
• at 2f: same size, real
• between 2f and f: larger, real
• at f: no image
• inside f: larger, virtual

Question 10

imaging rules for a diverging lens

Answer 10

1. a ray parallel to the principal axis is refracted as if it had come through the principal focus
2. a ray that appears through the secondary principal focus is refracted parallel to the principal axis
3. a ray through the optical centre continues straight on its path

Question 11

images in a diverging lens

Answer 11

always smaller, upright, same side, and virtual

Question 12

lens equation

Answer 12

1/f = 1/do + 1/di

Question 13

magnification equation

Answer 13

M = hi/ho or M = -di/do

Question 14

positive variables

Answer 14

• do always
• di real image / opposite side
• ho when measured upward
• hi when measured upward
• f for converging
• M for upright

Question 15

negative variables

Answer 15

• do never
• di virtual image / same side
• ho when measured downward
• hi when measured downward
• f for diverging
• M for inverted

Question 16

the camera

Answer 16

device that takes light from large, distant objects (beyond 2f) to form smaller, real images on either film or a sensor

users cannot move film to get sharp images, so they focus

Question 17

the movie projector

Answer 17

takes a small object (between f and 2f) and projects a large, inverted, real image on a movie screen

Question 18

the magnifying glass

Answer 18

a converging lens where the object is played in between f and the lens, the refracted rays diverge and the brain extends these rays backward and produces an enlarged, virtual image

Question 19

the compound microscope

Answer 19

an arrangement of two converging lenses that produces two enlarged, inverted images, one real, one virtual; the real image is formed by the objective lens inside the body tube of the microscope, and the virtual image is formed by the eyepiece lens which is visible to see

Question 20

the refracting telescope

Answer 20

same concept as a compound microscope, but the object is much farther away beyond 2f (incident rays are seen as parallel), it produces two enlarged, inverted images (one real not seen inside the tube and the larger virtual seen image)

Question 21

pupil

Answer 21

the black opening in the middle of the coloured part of the eye (iris), the pupil gets bigger or smaller in response to changes in light, muscles in the iris control size, and it lets light into the eye

Question 22

cornea

Answer 22

the transparent part of the eye that covers the front portion (covers the iris, pupil, and anterior chamber), the main function is to refract or bend light and is responsible for focusing most of the light entering the eye

Question 23

iris

Answer 23

the coloured part of the eye, iris muscles control the pupil (black opening that legs light into the eye), and the colour of an iris is unique to each individual, like a fingerprint

Question 24

lens

Answer 24

a neatly transparent biconvex structure behind the iris, sole function is to focus light rays onto the retina, is made up of unusual elongated cells that have no blood supply but obtain nutrients from the surrounding fields

Question 25

retina

Answer 25

a key bridge between the light that embers the eye and images seen, cells in the retina react to light and pass signals to your brain to see

Question 26

how does someone see an image

Answer 26

upside down, but the brain flips it right side up

Question 27

accommodation

Answer 27

the changing of shape of the eye lens by eye muscles to allow a sharply focused image to form on the retina

Question 28

hyperopia

Answer 28

the inability of the eye to focus light from near objects; far sightedness fixed with a positive meniscus (converging lens)

Question 29

presbyopia

Answer 29

a form of far-sightedness caused by a loss of accommodation as a person ages

Question 30

myopia

Answer 30

the inability of the eye to focus light from distant objects; near-sightedness fixed with a negative meniscus (diverging lens)

Question 31

optic nerve

Answer 31

relays messages from your eyes to your brain to create visual images, play a crucial role in your ability to see, millions of nerve fibres make up each optic nerve, damage to an optic nerve can cause vision loss

Question 32

astigmatism

Answer 32

A common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision, occurs when the front surface of the eye or the lens has mismatched curves (instead of a curve like a ball, the surface is egg shaped causing blurred vision at all distances)

Question 33

colour blindness

Answer 33

more accurately poor or deficient colour vision, is an inability to see the difference between certain colours (true colour blindness where everything is seen in black-and-white is rare), normally it is inherited and most people with colour blindness cannot distinguish between certain shades of red and green

Question 34

what causes colour blindness

Answer 34

if cone cell in eyes lack one or more wavelength sensitive chemicals, the eye will be unable to distinguish the colours red, green, or blue, as chemicals in the cones trigger a reaction and send the wavelength information through your optic nerve to your brain

Question 35

what is laser eye surgery

Answer 35

- the most commonly practiced procedure to correct vision problems caused by refractive errors (such as hyperopia, myopia, and astigmatism) - a surgeon uses a laser device to make permanent changes to the shape of the cornea (most commonly the excimer laser)