Light

Question 1

What is the aqueous humour?

Answer 1

Lies between the cornea and the lens. It is a clear, watery fluid produced by the ciliary body to lubricate the lens and cornea.

Question 2

What is the cornea?

Answer 2

Bends light into the lens. Lies in front of the iris. Is clear.

Question 3

What is the lens?

Answer 3

A flexible structure that enables light to be focused on the retina.

Question 4

What is the ciliary body?

Answer 4

The lens is connected to the ciliary body. Muscles in the ciliary body change the shape of the lens.

Question 5

What is the conjunctiva?

Answer 5

A membrane that covers the sclera.

Question 6

What is the choroid?

Answer 6

Has a rich blood supply and nourishes the retina.

Question 7

What is the sclera?

Answer 7

White of the eye.

Question 8

What are the eye muscles?

Answer 8

Enable the eye to rotate in its socket.

Question 9

What is the vitreous humour?

Answer 9

Clear fluid between the lens and retina.

Question 10

What is the optic nerve?

Answer 10

Carries the electrical signals from the retina to the brain.

Question 11

What is the fovea centralis?

Answer 11

Responsible for sharp central vision. Cone cells are more concentrated in the fovea centralis - the areas of sharpest vision. Rod cells are located on the retina.

Question 12

What is the dilator muscle?

Answer 12

Enlarges the pupil, allowing more light into the eye.

Question 13

What is the iris?

Answer 13

The coloured part of the eye - it contains the dilator muscles and sphincter muscle as part of its structure.

Question 14

What is the sphincter muscle?

Answer 14

Makes the pupil smaller, which stops light entering the eye.

Question 15

What is the pupil?

Answer 15

An opening in the iris that determines the amount of light entering the eye.

Question 16

How do the lenses of your eyes focus on close and far objects and what is this called?

Answer 16

Close- when the muscles attached to the lens relax, the lens gets much fatter and bends light more, allowing close objects to become more focused.

Distant- when the muscles attached to the lens contract, the lens stretches, becoming quite flat, allowing the lens to focus on more distant objects.

This is called accomodation.

Question 17

How do vision problems occur?

Answer 17

As people age, peoples lenses harden, making accomodation of their lenses more difficult. This means they can’t focus on short or long sighted things as well as the other sighted distance.

Question 18

How do people see an unclear image?

Answer 18

When light isn’t focused to a point at the retina.

Question 19

What is short sightedness generally known as?

Answer 19

Myopia.

Question 20

What is long sightedness generally known as?

Answer 20

Hyperopia.

Question 21

What is a convex lens and what are its effects?

Answer 21

A lens which bulges outward. This causes light rays to come together, or converge.

Question 22

What is a concave lens and what are its effects?

Answer 22

A lens which curves inwards. This causes light to diverge, or spread out.

Question 23

List the waves of the Electromagnetic Spectrum in order from longest to shortest.

Answer 23

1. Radio Waves
2. Micro Waves
3. Infrared Rays
4. Visible Light
5. Ultraviolet Rays
6. X-Rays
7. Gamma Rays

Question 24

Define Frequency.

Answer 24

The number of waves produced each second. Measured in Hertz (Hz) which means Waves per second.

Question 25

Define Amplitude.

Answer 25

The maximum displacement a particle can achieve from the middle line (affects brightness of light).

Question 26

What is the relationship between the wavelength of a wave and the amount of energy it has?

Answer 26

The shorter the wavelength and the higher the frequency, the more energy is carried by the radiation. The longer the wavelength and the lower frequency, the less energy is carried by the radiation.

Question 27

List at least 2 uses of each wave from the Electromagnetic Spectrum.

Answer 27

Radio Waves:

• T.V.
• F.M. Radio

Microwaves:

• telephone communication
• to heat food

Infrared Rays:

• T.V. Remotes
• night vision for cameras

Visible Light:

• sunlight
• fluorescent light

Ultraviolet Rays:

• U.V. Lamps
• for tanning booths

X-Rays:

• to look at bones
• to look for tumours

Gamma Rays:

• to kill cancer cells
• to sterilise medical equipment

Question 28

What happens when objects get very hot?

Answer 28

Thermal equilibrium / it produces its own light.

Question 29

What is the speed of light?

Answer 29

299 792 458 metres per second / 300 000 km per second.

Question 30

Define translucent.

Answer 30

A substance that allows light, but not detailed shapes to pass through e.g. Butter paper and ground glass.

Question 31

Define transparent.

Answer 31

A substance that allows light to pass through so that the objects behind can be seen distinctly e.g. Glass and air.

Question 32

Define opaque.

Answer 32

A substance that does not allow any light to pass through, and blocks off all light and cannot be seen through e.g. Brick and wood.

Question 33

Define luminous.

Answer 33

An object which gives off light e.g. The sun, a lighted candle and a light bulb.

Question 34

Define non-luminous.

Answer 34

An object which isn’t capable of producing light, but can be capable of reflecting light off a different source e.g. The moon, a table and a chair.

Question 35

What is the law of reflection?

Answer 35

A law which states that the angle of incidence and the angle of reflection are the same. i=r.

Question 36

What is refraction?

Answer 36

The change of direction of a ray of light in passing obliquely from 1 medium to another in which it’s wave velocity is different.

Question 37

List the colours of the visible light in order from longest to shortest wavelength.

Answer 37

1) Red light (650nm)
2) Orange light (590nm)
3) Yellow light (570nm)
4) Green light (510nm)
5) Blue light (475nm)
6) Indigo light (445nm)
7) Violet light (400nm)

Question 38

Why do we see objects in colour?

Answer 38

Light containing all wavelengths emitted from a light source. Light travels through space until it strikes a coloured object (green). All wavelengths of light except green wavelengths of light are absorbed by the object. Green wavelength is reflected off the object. Light of green wavelengths travels through space entering the eye. Light strikes retina in the eye and we see a green object.

Question 39

List the primary colours of light.

Answer 39

Red, green and blue.

Question 40

List the secondary colours of light.

Answer 40

Magenta, cyan and yellow.

Question 41

What colour do you get when all light wavelengths are together?

Answer 41

White light.

Question 42

If you were in a pitch black room and viewed a red apple under a green light, what colour would that apple appear and why?

Answer 42

The apple would appear black because the green would be absorbed and there would be no red light to be reflected. Black appears when all light wavelengths are absorbed. That is why the apple would appear black.

Question 43

What happens to the lens when the eye focuses on close objects?

Answer 43

For close objects, light rays need bending more compared to those from distant objects to form a clear image. Therefore, ciliary muscles relax causing lens to take a short, fat shape which bends the light rays more, focusing a clear image on the retina.

Question 44

What happens to the lens when the eye focuses on distant objects?

Answer 44

For distant objects, light rays do not need bending as much as those from close objects to form a clear image. Therefore, ciliary muscles contract causing lens to take a thin, tall shape which bends the light rays less, focusing a clear image on the retina.