11B - So so sorry! But here is the spec for P6 anyway!

Hello Chaps.

I'm so sorry you didn't get this before your test today... I lost my password and it has taken me an age to work it out (I'm putting it down to old age creeping up on me!)

Anyway I was going to try and remind you of areas that have been covered by pasting in the specification for this bit.... AS EVER IF YOU GET STUCK... COME IN AND GET IT SORTED!!!

This will be useful for your revision notes for the main exams anyway so here goes:

What are waves?
1. recall that a wave consists of disturbances that transfer energy in the
direction that the wave travels, without transferring matter;
2. describe the differences between a transverse and a longitudinal wave;
3. recall that the frequency of the waves, in hertz (Hz), is the number of
waves each second that are made by the source, or that pass through
any particular point in the medium;
4. recall that the wavelength of waves is the distance between the same
point on two adjacent disturbances;
5. recall the amplitude of waves is the distance from the top of the crest or
bottom of the trough to the undisturbed position;
6. draw and interpret diagrams showing the amplitude and the wavelength
of waves;
7. use the equation:
• wave speed = frequency x wavelength
(metre per second m/s) (hertz, Hz) (metre, m)
􀁌 Rearrangement of the equation is only expected on the higher tier.
8. recall that the speed of a wave is usually independent of its frequency
and amplitude.

Why do scientists think that light and sound are waves?
1. draw and interpret diagrams showing the reflection of plane water waves
and narrow beams of sound or light from a plane reflector;
2. recognise that wave speed is affected by what waves are travelling along
or through (the medium) and that the speed will change if a wave moves
from one medium into another;
3. explain how a change in the speed of a wave causes a change in
wavelength since the frequency of the waves cannot change, and how
this may cause a change in direction;
4. draw and interpret diagrams showing the refraction of plane water waves,
or beams of light or sound, when they cross a boundary between
different media, relating the change of direction to the change in wave
speed;
5. recall that the refraction of light waves and sound waves can be
explained by a change in their speed when they pass into a different
medium;
6. recall that light rays for which the angle of refraction would be greater
than 90 degrees cannot leave the medium they are in, and are reflected
and that this is known as total internal reflection;
7. recall that waves can spread out at a narrow gap and that this is called
diffraction;
8. draw and interpret diagrams showing wave diffraction through gaps;
9. recall that light can be diffracted but needs a very small gap, comparable
to the wavelength of the wave;
10. recall that where two waves meet, their effects add and that this is called
interference;
11. recall that where two waves arrive in step they reinforce and where they
arrive out of step they cancel out;
12. recall that two light beams can be shown to produce an interference
pattern;
13. explain interference patterns in terms of constructive and destructive
interference;
14. explain how the diffraction and interference of light and sound are
evidence of their wave natures.

Do all types of electromagnetic radiation behave in the same way?
1. recall that the different colours of light in the spectrum have different
frequencies (and therefore wavelengths);
2. list the parts of the whole electromagnetic spectrum in order of frequency
or wavelength (radio waves, microwave, infrared, visible light, ultraviolet ,
X-rays, gamma radiation);
3 recall that the energy delivered by each photon in a beam of
electromagnetic radiation increases with the frequency of the
electromagnetic waves;
4. understand that the intensity of a beam of electromagnetic radiation (the
energy it delivers per second) depends on the number of photons arriving
every second and the amount of energy carried by each photon;
5. know that all types of electromagnetic radiation travel at exactly the
same, very high, speed through space (a vacuum);
6. recall an important difference between electromagnetic waves and sound
waves: electromagnetic waves can travel through empty space, but
sound waves can only travel through a substance (solid, liquid or gas);
7. understand that different frequencies of electromagnetic radiation are
used for different purposes due to the difference in reflection, absorption
or transmission by different materials to include:
• radio waves are not strongly absorbed by the atmosphere so can be
used to carry information for radio and TV programmes;
• some microwaves are strongly absorbed by water molecules and so
can be used to heat objects containing water;
• satellite dishes are made of metal because metals reflect
microwaves well;
• X-rays are absorbed by dense materials so can be used to produce
shadow pictures of bones in our bodies or of objects in aircraft
passengers’ luggage;
• light and infrared radiation can be used to carry information along
optical fibres because they travel through without becoming
significantly weaker.

How is information added to a wave?
1. recall that signals can be carried not only by radio waves and
microwaves through the Earth’s atmosphere and through space but also
by light waves and infrared waves through optical fibres;
2. understand that if a wave is to carry information the waves must be made
to vary in amplitude or frequency, and that the information is carried by
the pattern of the variation, recall that this process is called modulation;
3. interpret diagrams showing how a sound wave can be used to vary the
amplitude or frequency of a radio wave, with a pattern that matches its
own frequency;
4. recall that a signal which varies continuously is called an analogue
signal;
5. recall that the job of the receiver is to reproduce the original sound from
the pattern of the variation;
􀁌 Details of any transmission or receiver systems are not required.
6. recall that sound (or other information) can be transmitted digitally (digital
signal);
7. recall that, in digital transmission, the sound is often converted into a
digital code made up from just two symbols (0 and 1);
8. recall that this coded information can be used to control the short bursts
of waves (pulses) produced by a source (0 = no pulse, 1 = pulse);
9. recall that when the waves are received, the pulses are decoded to
produce a copy of the original sound wave;
10. know that an important advantage of digital signals over analogue signals
is that they can transmit information with higher quality, i.e. the signal is
less affected by the transmission process;
11. understand that all signals, as they travel, decrease in intensity (their
amplitude becomes smaller), so they may have to be amplified;
12. know that random additions to the original signal (noise) may be picked
up as a signal travels, reducing its quality;
13. know that, when a signal is amplified, any noise it has picked up is also
amplified;
14. understand that, with digital signals, ‘on’ and ‘off’ states can usually still
be recognised despite any noise that is picked up. The signal can
therefore be cleaned up to remove the noise and restore the original
pattern of ‘on’s and ‘off’s;
15. be able to use these ideas to interpret information about analogue and
digital transmission and to explain why information can be
transmitted digitally with higher quality.


Hmmm... have fun with this... remember if it's not written on the above you can't be tested on it!