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AVERAGE SPEED
When calculating the AVERAGE SPEED of an object
you need to know the DISTANCE travelled by the
object and the TIME taken to travel that distance. You
then use the following equation:
average speed = distance
time
V =
d
t
Where v – average speed (m/s)
d - distance (m)
t - time (s)
L.I:
To calculate the average speed of a
trolley on a slope
APPARATUS:
slope, trolley, timer,meter stick
METHOD:
measure distance on slope
release trolley and start timer together
stop timer when trolley reaches 2m mark.
complete table.
RESULTS:
ATTEMPT
1
2
3
TIME
(S)
SPEED OF SOUND
LEARNING
INTENTION
To calculate the speed of sound
experimentally.
APPARATUS
fast timer, 2 microphones, metre stick
METHOD
Place the 2 microphones 1m apart. Switch on
timer. Clap hands above start microphone.
Record time in table. Repeat twice more.
Calculate average time using v = d/t.
RESULTS
Attempt
1
2
3
CONCLUSION
Speed of sound equals 340m/s.
Time (s)
2903
2738
3236
SOUND AND LIGHT
The speed of light is much faster than the speed of sound.
Think of a thunder storm. You see the lightning then you
hear the thunder. This is because the light reaches us
almost immediately.
The values we need to know are:
Speed of sound = 340m/s
Speed of light = 300000000m/s
The equation we use is:
Distance = speed x time
d
d=vt
v
t
MORSE CODE
In 1836, Samuel Morse demonstrated the
ability of a telegraph system to transmit
information over wires. The information
was sent as a series of electrical signals.
Short signals are referred to as dits
(represented as dots). Long signals are
referred to as dahs (represented as
dashes). With the advent of radio
communications, an international version
of Morse code became widely used.
TELEPHONE
The most common method of communicating
with wires is the telephone. The TRANSMITTER
(mouthpiece) contains a MICROPHONE which
changes sound energy to electrical energy. The
RECEIVER (ear piece) contains a loudspeaker
that changes electrical energy into sound energy.
SOUND SIGNALS
Sound signals are transmitted down wire at almost
300000000 m/s (speed of light) and the signals can be
displayed using an oscilloscope as shown:
WAVES
Messages can be sent from one place to another by using
waves. They are sent from a transmitter to a receiver. You
will have heard of radio, tv and microwaves.
A typical wave pattern is shown below:
SPEED OF A WAVE
To calculate the speed of a wave we use the equation:
V=fx
v
f
Where v = velocity (m/s)
f = frequency (Hz)
 = wavelength (m)

WAVE DEFINITIONS
Frequency:
Wavelength:
The number of complete waves that pass a
point every second. Symbol f, units – hertz
(hz).
The distance from a point on a wave to the
next similar point – from crest to crest.
Symbol  (lambda), units - metres (m).
Wave speed:
The distance a wave travels each second.
Symbol v, units – metres per second (m/s)
Amplitude:
The maximum height of the wave above
or below the zero line. Units – metres (m).
RADIO
Transmitter mast
Old fashioned receiver
Radio signals are waves that transfer energy. They are
sent from a transmitter at a speed of 300000000m/s and
picked up by a receiver. Wires are not needed between
the transmitter and the receiver.
RADIO TRANSMITTER
Radio frequency
Modulator
Amplifier
Aerial
Audio frequency
Modulator:
combines the 2 electrical signals
Amplifier:
makes the combined signal bigger
Aerial:
changes electrical signal into a radio
wave and sends them in all
directions.
RADIO RECEIVER
Aerial
Tuner
Decoder
Amplifier
Loudspeaker
Power supply
Aerial:
Tuner:
Decoder:
Amplifier:
Picks up all radio waves.
Selects the frequency you want.
Separates the radio wave from the sound wave.
Makes the weak signal stronger.
Power supply:
Loudspeaker:
Needed for amplifier.
Changes electrical signal to sound.
TELEVISION RECEIVER
Aerial
SOUND
Decoder
Amplifier
Loudspeaker
Decoder
Amplifier
Tube
Tuner
VISION
Aerial:
Picks up all wave energy.
Tuner:
Selects the TV frequency you want.
SOUND
Decoder:
VISION
Selects the sound signal
from wave.
Decoder:
Selects the picture
signal from wave.
Amplifier: Makes the sound signal
stronger.
Amplifier: Makes the picture
signal stronger
Loudspeaker: Changes electrical
signal to sound.
TV Tube: Changes electrical
signal to light
TV TRANSMITTER
High frequency signal
Modulator
Amplifier
Audio signal
Aerial
High frequency signal
Modulator
Amplifier
Camera (video)
Modulator:
combines high frequency signals with audio
and video signals.
Amplifier:
electrical signals are made stronger.
Aerial:
signals are changed to TV and radio waves.
TV TUBE & LINE BUILD UP
A tv picture is built up by a series
of lines. An electron beam scans
across the television tube
(electromagnetic deflection). A
special coating gives out light
when the beam passes over it.
The beam starts at the top then
scans backwards and forwards till
it reaches the bottom. There are
625 lines for one picture and 25
pictures per second.
COLOUR TV
In a colour tv there are three electron guns. There are
three colours of light given out by the fluorescent paint on
screen. These are red, green and blue. All colours can be
made by mixing these three :yellow
-
red & green
magenta
-
red & blue
cyan
-
green & blue
white
-
red, blue & green
Colour tv
AMPLITUDE MODULATION
Amplitude modulation is a way of varying the amplitude of a
high frequency radio wave so that it carries a low frequency
audio wave
Low frequency
audio wave
Carrier wave
Amplitude
modulated wave
AM WAVE
FM WAVE
DIFFRACTION
LEARNING INTENTION
Waves with a long wavelength can bend round or over
obstacles much better than short wavelengths.
LONG WAVELENGTH
SHORT WAVELENGTH
Radio waves have a longer wavelength than TV waves. This is
why in some hilly regions you can receive good radio reception
but not a good tv picture.
LAW OF REFLECTION
LEARNING
INTENTION
To investigate the relationship between
the angle of incidence and the angle of
reflection for a plane mirror.
APPARATUS
Power supply, ray box, mirror, singleslit and a protractor.
INSTRUCTIONS
Mirror
80o
60o
30o
10o
N
RESULTS
Angle of incidence Angle of reflection
10o
30o
60o
80o
CONCLUSION
The angle of reflection is equal to the
angle of incidence.
OPTICAL FIBRES
• An optical fibre is a thin piece of glass.
• Optical fibres are used in some
telecommunication systems. They are
used to transmit light signals.
• Signal transmission along an optical
fibre takes place at a speed of
200 000 000m/s
OPTICAL FIBRES 2 cont.
• The transmission of the light signal along an
optical fibre works by reflection inside the
fibre.
• Many telecommunication links into the home, like cable
TV, use optical fibres.
• Fibre optics are cheaper than copper cables, however,
they are difficult to join together.
TOTAL INTERNAL REFLECTION
LEARNING
INTENTION:
To find out about TOTAL INTERNAL
REFLECTION.
APPARATUS:
Ray box, single slit, semi-circular block & protractor
METHOD:
Set up apparatus as shown.
Send a single beam along 20o line.
Draw path of ray.
Repeat for an angle of 60o
Complete table.
60o
20o
Ray box
RESULTS
Angle of incidence
20o
60o
Does any light Is any light reflected
pass into air? back into perspex
YES
NO
YES
YES
CONCLUSION:
When no light passes from the
perspex to the air, we have
TOTAL INTERNAL
REFLECTION taking place
SATELLITES
• Satellites are used to send information from one
part of the world to the other.
• A geostationary satellite is one that stays above the
same point on the earth’s surface (36000km).
• Curved reflectors on receiving aerials make the signals
stronger.
• The curved reflectors gather the signals and reflect
them to a focus which makes them stronger.
CURVED REFLECTORS
Learning Intention:
How curved reflectors make signals stronger
RAYBOX