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Flashcards in HEALTH Light And Sight Deck (32):
0

Light is focused by the ____ and the _____. Most of the refraction takes place at the _____. The ____ changes shape and allows the eye focus on objects at different distances.

Light is focused by the CORNEA and the LENS. Most of the refraction takes place at the CORNEA. The LENS changes shape and allows the eye focus on objects at different distances.

1

What is refraction?

The bending of light/change of speed as it passes from one material to another.

2

When light passes from air into glass, light bends _____ the normal and when it passes from glass to air it bends _____ from the normal.

When light passes from air into glass, light bends TOWARDS the normal and when it passes from glass to air it bends AWAY the normal.

3

Concave

Bends in

4

Convex

Bends out

5

How do convex affect light?

Brings the light to a fous

6

How does concave lens affect light?

Spreads it out

7

How is the image formed on the retina different to the real object?

Image is formed upside down, back to front and smaller

8

What is focal length?

The distance between a lens and the point where parallel rays of light are brought to a focus.

9

Describe an experiment to measure focal length

Put e lens i front of a screen and move e lens until a sharp image if distance object is obtained on the screen. Measure the distance from the lens to the screen and this is the focal length,

10

Short sighted people can't focus on _____ objects clearly.

Distant

11

Long sighted people can't focus on _____ objects clearly.

Close

12

What type of lens corrects short sighted vision?

Concave

13

What type of lens corrects long sighted vision?

Convex

14

What type of light do fibre optic transmit?

Cold light (no heat is transmitted)

15

What is angle of incidence?

Angle between ray and normal.

16

What is the angle of refraction?

Angle between refracted ray and normal.

17

What is the normal?

The perpendicular line that passes thought the angle of incidence and angle of refraction.

18

What is short sighted in terms of light rays?

Light rays are brought to a focus before the retina.

19

How would a concave lens help to fix short sighted ness?

Would spread rays out so that they focus on retinia

20

What is long sighted in terms of light rays?

Light rays brought to a focus behind the retina.

21

Why would a convex lens solve long sighted ness.

Convex lenses converge the rays so that they focus on the retina.

22

What is the unit of measurement for the power of a lens?

Dioptres.

23

What is focal length measured in?

Meters

24

_____ lenses have a positive power (+)
_____ lenses have a negative power (-)

Convex lenses have a positive power (+)
Concave lenses have a negative power (-)

25

What are optic fibres used for?

To see inside a patients body without surgery.

26

What are optic fibres used for? (The appliance)

Endescope

27

Explain how an endoscope works

One bundle of fibres carry the cold light into the patient. The second bundle of light brings this reflected flight back to the surgeon's eye. the bundles are flexible so can move around inside the patient.

28

Is the angle of incidence less or more an the angle of refraction?

Less

29

Does a thin lens or thick lens have a longer focal length?

Thin

30

How does the eye focus on ne'er and distant objects?

The lens changes shape. For example to view near objects the muscles change the lens shape to thick.

31

What are the advantages if endescopes?

Cold light sources and small incision means faster recovery.