WAVES
Light Yr
8 Visible
light is a small part of the electromagnetic
spectrum Properties
of light (i) it
travels in straight lines (ii) it
travels at a finite
speed
through a uniform medium (iii) it
can travel through a vacuum Reflection Yr
8 Reflection
of light is a change in direction of the light when it
strikes a surface or mirror Use of the
quantitative relationship: angle
of incidence (i) = angle of reflection (r) § The
electromagnetic spectrum Yr
9 1. The
electromagnetic spectrum is the name given to the entire
range of frequencies and wavelengths of electromagnetic
(e.m.) waves (i) All
e.m. waves are the same form of radiant
energy. (ii) All
e.m. can travel through a vacuum.
(iii) All
e.m. waves travel at the same speed through vacuum (they all
travel at the speed
of light,
300,000,00 m/s) (iv)
Objects that absorb
e.m. radiation become hotter. 2. You
should know the names of the different parts of the e.m.
spectrum, and their relative position in the electromagnetic
spectrum. These are : radio
waves,
microwaves,
infrared
waves,
visible
light,
ultraviolet
waves,
X-rays,
gamma
rays 3.
Spectrum
of white light. § Characteristics
of waves Yr
10 1. Waves transfer
energy
but not matter. 2. All regular waves have
frequency,
wavelength
and amplitude. (i) Frequency (f)
is the number of waves produced per second. The unit of
frequency is the hertz (Hz) (ii) Wavelength is the
distance (in metres) between consecutive crests (or troughs)
in a transverse wave (iii) The amplitude of a
transverse wave is the maximum displacement from the mean
position in of the wave. 3. You must be able to
recall and use the wave
equation: 4. All waves can be
reflected,
refracted
and diffracted. questions
on Wave
properties § questions
on wave calculations Electromagnetic
waves Longitudinal
and transverse waves Yr
10 Examples of
longitudinal
waves and
transverse
waves, limited
to (i) sound
(a longitudinal wave) (ii) light
(a transverse wave) (iii) water (a transverse
wave) (iv) ropes (a transverse
wave) (v) springs (either
transverse or logitudinal waves) Refraction Yr
10 1. Refraction
of light is the change in direction of a wave when it passes
from one medium to another. 2. The cause of refraction
is the change in the speed of the wave when it passes from
one medium to another 3. You must be able to
draw diagrams showing the path of a narrow beam of light
when it refracts as it travels from air to glass or water.
(You will not be
asked to carry out calculations involving
refraction) § Total
internal reflection Yr
10 1. You should know what
total
internal reflection
is and the conditions in which it occurs. 2. You should know that
total internal reflection occurs when the critical
angle is exceeded.
(you will not be asked to carry out calculations involving
total internal reflection) 3. Uses of total internal
reflection, limited to: (i) optical
fibres (ii) reflecting
prisms Diffraction Yr
10 1. Diffraction
occurs when waves pass through a narrow gap or move past an
object. Waves spread beyond the gap or into the shadow of an
object when the wavelength about the same as the object's
size. 2. Diffraction is a
property of both light and sound waves. 3. Diffraction increases
with increasing wavelength. 4. Consequences of
diffraction applied to sound waves & radio
signals § Uses
and dangers of e.m. waves Yr
10 1. Effects of
absorption
of electromagnetic energy: (i) heating (ii) inducing
a.c.
of same frequency as incident wave. 2. Uses of microwaves,
infrared waves and ultraviolet waves in domestic situations,
limited to (i) cooking (ii) remote
control (iii)
sun-tanning 3. Dangers of
microwaves,
infrared
waves and ultraviolet
waves, limited to (i) heating
effects (ii) sunburn 4. Uses of
X-rays
and gamma
rays in medicine,
limited to (i) X-ray
photography (ii) sterilisation of
medical instruments (iii) destruction of cells
in cancer treatment. questions
on the properties of Electromagnetic
waves § Signals Yr
10 1. Definitions of
analogue
& digital
signals. 2. Examples of analogue
and digital signals. 3. Deterioration of
signals with distance & 'noise'.
4. Advantage of digital
signals over analogue signals Sound
waves Yr
10 1. Sound
is the vibration of a medium. It is a longitudinal
wave. 2. You must know that
sound has the following properties: (i) Sound travels at a
finite speed through a uniform medium (ii) Its speed depends on
the density of the medium (iii) Sound can't travel
through a vacuum (iv) Sound can be
reflected, refracted & diffracted. 3. An echo is the
reflection of sound waves. 4. Due to diffraction
sounds can be heard in the shadow of obstacles such as
buildings. questions
on Sound
§ Measuring
sound Yr
10 1. Amplitude
is a measure of the energy carried by the wave 2. Amplitude of a sound is
a measure of its loudness § Microphones
& loudspeakers Yr
10 1. Use of microphones
and loudspeakers,
limited to microphones changing sound waves into a varying
electric current and loudspeakers changing the current back
into sound 2. Use of the
cathode
ray oscilloscope
(CRO) to display patterns of regular sound waves. § Ultrasound Yr
10 1. Ultrasound
are sound waves with a frequency above the audible frequency
range (i.e. more than 20,000 Hz) 2. Uses of ultrasound,
limited to: (i) fetal imaging in
obstetrics (ii) determining the depth
of water by echo-sounding, (iii) in industry for
cleaning & quality control. questions
on Ultrasound
§ Seismic
waves Yr
11 1. Some seismic
waves are
longitudinal (called P-waves)
and some are transverse (called S-waves).
They are created in the Earth by vibrations due to
earthquakes. 2. The Earth has a layered
structure with a core, a mantle surrounding the
core,
and a thin solid crust. 3. The composition and
nature of each layer. 1.
Properties of S and P waves. 2.
Evidence for the Earth's internal structure from seismic
wave patterns. Tectonics Yr
11 1.
Lithosphere
is made up of plates that move relative to one another due
to convection within the mantle. 2. Nature of
earthquakes
and volcanoes & their unpredictability. 3. Details of
Wegener's
theory of continental drift
and why geologists found it difficult to accept. 1 Relative
movement of tectonic plates are the cause of subduction,
volcanoes, sea floor spreading. 2 Evidence
for continental drift from periodic magnetic reversals
GCSE
syllabus: force & motion
GCSE syllabus: electromagnetism
Date Last
Modified: April
2003
Emanuel School, London SW11 !HS
All text and diagrams copyright of J.C.Naylor