This document provides an overview of wave physics, detailing types of waves (transverse and longitudinal), their properties (wavelength, amplitude, speed, frequency, and period), and how they transfer energy. It explains the behavior of light and sound waves, including reflection, refraction, diffraction, and the concept of red-shift in relation to the expanding universe and the Big Bang theory. Key formulas related to waves and measuring them, as well as the function of oscilloscopes in visualizing sound waves, are also presented.

1. Physics 1.5
JaskiratK

2. Physics - P1.5
Waves
A wave is something that transfers energy from one point to another.
There are two types of waves:
Transverse and longitudinal waves.
What Are Waves?
• Transverse Waves -
Most of the waves that you should know about are
transverse waves. With this type of wave, the
particles of the medium vibrate at right angles to
the direction that the energy travels. This is where
the name transverse comes from - it means
'across'. All of the electromagnetic waves are
transverse waves, as are water waves.
• Longitudinal Waves -
With sound waves, the energy travels along in the
same direction as the particles vibrate. This type
of wave is known as a longitudinal wave, so
named because the energy travels along the
direction of vibration of the particles.

3. These words are important as they can tell you many things about a wave.
Waves Definition
• Wavelength -
The distance from a
point to another point
where the wave begins
to repeat itself. This
could be the distance
from peak to peak or
trough to trough.
Wavelength is
measured in metres
(m) and has the
symbol λ.
• Amplitude -
The amplitude of a
wave is half the
distance from peak to
trough. It can also be
thought of as the height
of the wave from the
rest position (rest
position = in the middle
when the wave is not
moving up or down).
Amplitude is measured
in metres (m).
Amplitude is the letter
“a” in the diagram
below.
• WaveSpeed -
The distance covered
by a wave in 1
second. Speed is
measured in metres
per second (m/s or
ms-1).
• Frequency -
This is the number of
waves produced in 1
second by the source
producing the wave.
Frequency is measured
in Hertz (Hz) and has
the symbol f..
• Period-
The period of a wave is
the time taken for 1 wave
to be produced. It is also
the time taken for one
whole wave to pass a
point. Period is measured
in seconds.

4. Energy Transfer
Waves are vibrations that transfer energy from place to place without mater (solid, liquid or gas) being
transferred. Think of a Mexican wave in a football crowd – the wave moves around the stadium, while
each spectator stays in their seat, only moving up the down when its their turn.
Some waves must travel through a substance. The substance is known as the medium and it can be
solid, liquid or gas. Sound waves and seismic waves are like this. They must travel through a medium,
and it is the medium that vibrates as the waves travel through.
Other waves do not need to travel through a substance. They may be able to travel through a medium,
but they do not have to. Visible light, infrared rays microwaves, and other types of electromagnetic
radiation, are like this. They can travel through empty space. Electrical and magnetic fields vibrate as
the waves travel.

5. Wave Speed
The speed of a wave is related to its frequency and wavelength, according to this equation:
v = f x λ
• v = Wave speed in metres per second, m/s.
• f = Frequency in hertz, Hz.
• λ (Lambda) = Wavelength in metres, m.
v
f λ
v
f λ
v
f λ
v = f x λ
f = v / λ
λ = v / f

6. Frequency & Time Period
The frequency of a wave can be calculated using this equation:
Frequency =
1
𝑇𝑖𝑚𝑒 𝑃𝑒𝑟𝑖𝑜𝑑
f =
1
𝑇
Where:
• f = Number of waves produced by a source per second, measured in Hertz, Hz.
• T = Time it takes for one complete oscillation, measured in seconds, S.
All waves, including sound waves and electromagnetic waves, following this equation. For example, a
wave with a time period of 2 seconds has a frequency of 1 ÷ 2 = 0.5 Hz.

7. Light & Sound
Light travels as transverse waves and can travel through a vacuum. Sound travels as longitudinal
waves and needs to travel through a solid, liquid or gas: It cannot travel through a vacuum.
Light and sound can be reflected and refracted, just like water waves. Light and sound can also be
diffracted, just like water waves, but diffraction in light is less obvious than sound.
Light and sound both travel as waves, but they are not identical. This table summaries the similarities
and differences between them.
Property Light Sound
Type Of Wave Transverse Longitudinal
Travel Through Vacuum Yes No (Only Solid, Liquid & Gas)
Reflected Yes Yes
Refracted Yes Yes
Diffracted Yes Yes
Interfere Yes Yes
Go Round Corners No Yes

8. Reflection
Sound waves and light waves reflect from surfaces. Remember that they behave just like water waves
in a ripple tank. This is called the ‘Law Of Reflection’.
You can investigate the law of reflection using a light box of 36°, it will be reflected at the same angle of
36°.
The Angle Of Incidence = The Angle Of Reflection
An incident ray of light hits a plane mirror at an angle and is reflected
back off it. Both angles are measured from the normal. The normal is an
imaginary line at right angles to the plane mirror.
Smooth surfaces produces strong echoes then sound waves hit them,
and they can act as mirrors when light waves hit them. The waves are
reflected uniformly and light can from images.
The waves can:
- Be focused to a point, e.g
sunlight reflected off a concave
telescope mirror.
- Appear to come from a point
behind the mirror, e.g looking at
glass.
Rough surfaces scatter sound and
light in all directions. However,
each tiny bit of the surface still
follows the rule:
The Angle Of Incidence = The
Angle Of Reflection

9. Ray Diagrams
In a ray diagram, the mirror is drawn a straight line with thick hatchings to show which side has the
reflective coating. The light rays are drawn as solid straight lines, each with an arrowhead to show the
direction of travel. Light rays that appear to come from behind the mirror are shown as dashed straight
lines.
Make sure that the incident rays (the solid lines) obey the law of reflections: The Angle Of Incidence =
The Angle Of Reflection. Extend two lines behind the mirror. They cross where the image appears to
come from.
The image in a plane mirror is:
- Virtual (It cannot be touched or projected onto a screen).
- Upright (If you stand in front of a mirror, you look the right way up).
- Laterally Inverted (If you stand in front of a mirror, your left side seems to be on the right in the
reflection).

10. Refraction
Sound waves and light waves change speed when they pass across the boundary between two
substances with different densities, such as air and glass. This cause them to change direction and this
effect is called refraction. We can use water waves in a ripple tank to show this effect.
Refraction doesn’t happen if the waves cross the
boundary at an angle of 90° (called the normal) –
in this case, they carry straight on. The refraction
follows a regular pattern.
When light passes from air into semi-circular
blocks or Perspex, as seen as the next page.
The light enters the curved face of the block
directly, so no refraction is seen here. As you
increase the angle of incidence you see a greater
angles of reflection.
At a specific angle, the light ray will no longer
leave the block. At this point the angle of incidence
is called the critical angle. Any further increase in
the angle of incidence will mean the ray is
reflected, not refracted.
When white light passes from air into a triangular
prism, it is refracted as it enters, and then again as
it exits. As it leaves the prism, the different
wavelengths of the individual colours of light result
in different angles of refraction.
This splits white light into the seven colours of the
rainbow. This process is called dispersion. Red
light is refracted the least and violet is refracted
the most. Each colour of light can be called
‘Monochromatic’.

11. 1.
2.
3.

12. Diffraction
When waves meet a gap in a barrier, they carry on through the gap. However, the waves spread out to
some extent into the area beyond the gap. This is diffraction.
The extent of the spreading depends on how the
width of the gap compares to the wavelength of
the waves. Significant diffraction only happens
when the wavelength is of the same order of
magnitude as the gap.
So, for example:
- A gap much larger than the wavelength causes
little spreading and sharp shadow, e.g light
through a doorway.
- A gap similar to the wavelength causes a lot of
spreading with no sharp shadow, e.g sound
through a doorway.
Diffraction can sometimes be seen in waves in the
sea when they pas into a harbour opening as
shown in the diagrams. The wavelength in these
diagrams is represented as the distance between
the blue vertical lines:
Diffraction through a narrow gap.
Diffraction through a wide gap.

13. Measuring Waves
Waves can be measured in two different ways:
- Wavelength = Peak to Peak.
- Amplitude = Centre to Top
Frequency represents the number of waves per second.
- Higher the Frequency = Shorter Wavelength
- Lower the Frequency = Longer Wavelength
WaveSpeed Equation:
Frequency (Hz) x Wavelength (m) = WaveSpeed (m/s)
Frequency Equation:
WaveSpeed (m/s) ÷ Wavelength (m) = Frequency (Hz)
Wavelength Equation:
WaveSpeed (m/s) ÷ Frequency (Hz) = Wavelength (m)
Frequency (Hertz):
- 1mHz = 0.001 Hz
- 1Hz = 1 Hz
- 1KHz = 1,000 Hz
- 1MHz = 1,000,000 Hz

14. Oscilloscopes
An oscilloscope is a machine that shows the wave shape of an electrical signal. When connected to a
microphone they can show the wave shape of sounds. These diagrams show oscilloscope traces of
three sounds:
Sounds 1 & 2:
- The sound waves have the same frequency, so
the sounds have the same pitch.
- Sound 3 has a greater amplitude than sound 1,
so sound 2 is louder.
Sounds 2 & 3:
- The sound waves have the same amplitude, so
the sounds have the same loudness.
- Sound 3 has a greater frequency than sound 2,
so sound 3 is higher pitched.
The frequency of a sound is the number od oscillations (waves) per second as is measured in hertz
(Hz). It can be calculated by:
𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 =
1
𝑇𝑖𝑚𝑒 𝑃𝑒𝑟𝑖𝑜𝑑
The time period is the time taken to complete one
oscillation and is measured in seconds. So if the
time period of a sound wave is 0.01 seconds,
then the frequency is calculated as;
Frequency = 1 ÷ 0.01 = 100 Hertz
This would make a low pitched sound (Low
Frequency) as this is towards the bottom of our
audible range.
Big Amplitude = Big Volume
High Frequency = High Pitch
Amplitude has NO impact on pitch.
Frequency has NO impact on volume

15. Using Light
- Largest Waves = Radio Waves
- Shortest Waves = Gamma Rays
- Largest Wavelength = Lower Energy
- Shortest Wavelength = Higher
Energy

16. Red-Shift
Moving Away (Stretched Out):
- Longer Wavelength
- Lower Frequency
- Lower Pitch
Moving Towards (Squashed Together):
- Shorter Wavelength
- Shorter Frequency
-Higher Pitch
The position of the lines have changed because of the Doppler effect. Their wavelengths have
increased (and their frequencies have decreased.
Astronomers have found that the further from us a star is, the more its light is red-shifted. This
tells us that distant galaxies are moving away from us, and the further away a galaxy is, the
faster it’s moving away.
Since we cannot assume that we have a special place in the Universe, this is evidence for a
generally expanding universe. It suggests that everything is moving away from everything else.
Red Shift(ed):
Moving away, at the speed of light, lower pitch.
Blue Shift(ed):
Moving towards, at the speed of light, higher pitch.

17. The Big Bang Theory
Scientists have gathered a lot of evidence and information about the Universe. They have used
their observations to develop a theory call the Big Bang. The theory states that about 13.7 billion
years ago all the matter in the Universe was concentrated into a single incredibly tiny point. This
began to enlarge rapidly in a hot explosion, and it is still expanding today.
Evidence for the Big Bang theory:
- All the galaxies are moving away from us.
- The further away the galaxy is, the faster it’s moving
away.
Scientists have also detected a cosmic
microwave background radiation or
CMBR. This is received from all parts
of the Universe and is thought to be
the heat left over from the original
explosion.
These two features are found in
explosions – the fastest moving
objects end up furthest away from the
explosion.