Light & Sound Summary

Seite 1

SCIENCE

TOPIC TEST 2 REVISION: LIGHT AND SOUND

SECTION

ONE: Sound

SLO

01: Describe how

sound is generated and how sound travels through air

A

sound wave is created when an object vibrates and causes the air

around it to bunch up and then spread apart. Bunched up air particles

are called compression and particles spread out are called rarefaction. Rarefactions and compressions travel as a sound wave.

SLO

02: Describe

sound

as a waveform and relate amplitude

to loudness and pitch to frequency

The amplitude of a sound wave is the measure of how loud it is, and the frequency of a sound wave determines its pitch. The

substance that sound waves travel through is called a medium. Sound

waves can only travel through mediums with air, so there is no sound

in a vacuum (eg: space). How fast a sound wave travels depends on how

dense the medium it is traveling through is. The denser the medium

is, the faster the sound wave will travel, because there are more

particles in a dense substance.

SLO

03: Label a

diagram of the ear

Pinna, Ear Canal, Eardrum, Hammer, Anvil, Stirrup, Cochlea, Auditory Nerve, Eustachian Tube

SLO

04: Explain the

role of major components of the ear in the hearing process

Pinna- Focuses sound waves into the ear canal

Ear canal- Where sound travels through to the inner ear

Eardrum- A thin stretched piece of skin which resembles a drum, and where sound vibrations are received and passed on

Hammer, anvil & stirrup- 3 tiny bones which intercepts and passes on the vibrations

Cochlea- Translates the vibrations to a neural message

Auditory nerve- Sends the neural messages to the brain

SECTION

TWO: Seeing things

SLO

05: List important

properties of light (e.g. active form of energy, travels in straight

lines, fast)

Light

is an active form of energy which travels in straight light waves at

an amazing speed of 300,000 km/s.

SLO

06: Describe objects

as opaque, translucent and transparent

Opaque

objects do not let any light pass through. Translucent objects let a

little light through and transparent objects let all light pass

through them.

SLO

07: Distinguish between

a light source and a reflector and give

examples of

both.

A

light source is something that radiates its own light (eg a light

bulb) and a reflector does not radiate light but light bounces off on

its surface (eg a mirror).

SLO

08: Explain how

light sources and reflectors are seen by the eye.

We

can see light sources because some of the light waves shine directly

to our eyes, the other light rays bounce off other objects that are

reflective and to our eyes so we can see objects even if they do not

radiate their own light.

SECTION

THREE: Reflection

SLO

09: Draw a

simple ray diagram showing reflection off a flat surface.

SLO

10: Describe the

difference between regular (specular)

and diffuse reflectance.

Regular

reflection is when all the reflection rays bounce off in the same

direction. This is when light hits a smooth surface such as a mirror.

Diffuse reflection is when all the reflection rays bounce in

different directions. This happens when light hits an uneven surface

such as a gravel path.

SLO

11:

Distinguish between

concave and convex mirrors and draw simple ray diagrams showing

reflection off each type of mirror.

A concave mirror is a mirror which curves inward. Which light hits its surface, it is reflected inward toward a focal point. Therefore a concave mirror is a converging mirror. On the other hand, a convex mirror, which is a mirror which curves outward, reflects light outward, so convex mirrors are diverging mirrors.

SLO

12: State important

uses of plane, concave and convex mirrors.

Uses

of Concave mirrors

Uses

of Convex mirrors

Satellite

dishes

Car

headlights

Telescope

Car

wing mirrors

Security mirrors

SECTION

FOUR: Refraction

SLO

13: Describe the

process of refraction when light passes from one medium into another

and draw a

diagram to illustrate the effect.

SLO

14: Explain refraction

in terms of change in density of medium and change in light speed.

When

a light passes from one medium into a denser medium, the light slows

down at the boundary and the light ray bends towards the normal.

When

a light passes from one medium into a less dense medium, the light

speeds up at the boundary and the light ray bends away the normal.

SLO

15: Distinguish between

converging and diverging lenses and draw simple

ray diagrams for each type of lens.

Converging

lens (aka convex lens) is thicker in the middle while diverging lens

(aka concave lens) is thinner in the middle.

SLO

16: State important

uses of converging lenses and relate each use to the image produced.

Converging

lenses are used in magnifying glasses and binoculars because it makes

objects appear closer and clearer. Diverging lenses are used in

spectacles to correct near sightedness because it makes objects

appear smaller and farther away.

SLO

17: Label a

diagram of the eye.

Cornea, Iris, Pupil, Lens, Retina, Optic nerve, Vitreous humor

SLO

18: Explain the

role of major components of the eye in the viewing process.

Cornea- Acts as the "window" of the eye, lets light in

Iris- Contracts and dilates the pupil to control the amount of light entering. Is pigmented so light cannot pass through

Pupil- A hole which light passes through

Lens- Changes its shape to focus on objects at various distances

Retina- Receives and translates light focused by the lens into neural messages. Is responsible for seeing color

Optic nerve- Sends the neural messages to the brain

Vitreous humor- A gel-like liquid which helps the eyeball maintain its shape and structure

SECTION

FIVE: Colour

SLO

19: Name,

in order, the colours of the rainbow (ROY G BIV).

Red,

orange, yellow, green, blue, indigo, violet

SLO

20: Draw a

diagram showing dispersion of light by a prism with the colours in

correct order.

SLO

21: Name the

three primary colours and state the colours produced when pairs of

primary colours are mixed (includes white for all three and black for

none).

The

primary colours of light are: red, blue and green. When red and blue

are mixed, we get a magenta colour. If blue and green are mixed, we

get a cyan colour, and when red and green are mixed, we get a yellow

colour. If all three are mixed, we get a white light, and if no

colours are present we see black.

SLO

22: Explain how

the eye uses the three primary colours to sense all colours and their

shades.

When

light hits the surface of an object, some colours are reflected and

some colours are absorbed.

SLO

23: Explain the

colour of an object in terms of selective absorption and reflection

of primary colours.

When

light hits the surface of an object, colours that make up the colour

of the object is reflected while other colours are absorbed. For

example if cyan (blue and green light) light hits the surface of a

magenta (blue and red) mug, green is absorbed and blue is reflected,

so the magenta mug appears to be blue under a cyan light.