November: 13-17

states that when an object is bent, stretched or compressed by a displacement s, the restoring force F is directly proportional to the displacement - provided the elastic limit is not exceeded.

A body is said to be moving with simple harmonic motion if:

(i) its acceleration is directly proportional to its distance from a fixed point on its path and

(ii) its acceleration is always directed towards that point

• A mass vibrating up and down at the end of a spring moves with SHM.

• Each prong on a vibrating tuning fork moves with SHM.

• The projection of uniform circular motion on a diameter is SHM

• For a small angle of swing a pendulum moves with SHM.

•The tides coming in and out every 6 hours move with SHM

•A magnet suspended horizontally from a piece of thread moves with . SHM if it is displaced slightly from being aligned North-South

w = √(k ÷ m)

The measure of the hotness or coldness of a body

Any physical property that changes measurably with temperature

• Length of a column of liquid

• Electrical resistance

• Emf of a thermocouple

• Colour

• Volume of a gas at constant pressure

• Pressure of a gas at constant volume

*Learn*

They will agree at 0 °C and 100 °C

They generally disagree at other temperatures because Thermometric Properties do not change proportionally with the same change in the degree of hotness

Each thermometer is correct on its own scale. No one reads the 'true value' for the temperature

The heat capacity of an object is the heat energy needed to change its temperature by 1 K (1 °C)

The specific heat capacity (c) of a substance is the heat energy needed to change the temperature of one kilogram of that substance by one kelvin

The latent heat (L) of a substance is the heat energy needed to change its state without a change in temperature

The specific latent heat (l) of a substance is the amount of heat energy needed to change the state of 1 kg of that substance without a change in temperature

The specific latent heat of fusion of a substance is the amount of heat energy needed to change 1 kg of that substance from a solid to a liquid without a change in temperature (i.e. at its melting point)

The specific latent heat of vaporisation of a substance is the amount of heat energy needed to change 1 kg of that substance from a liquid to a gas without a change in temperature (i.e. at its boiling point).

*Learn Diagram*

Transfers energy from a cooler region to a warmer one. Work must be done to bring this about. It is used in refrigerators and in air conditioning systems in buildings and cars.

The circulating liquid has a high specific latent heat of vaporisation and a low boiling point

the movement of heat energy through a substance by the passing on of molecular vibration from molecule to molecule. There is no overall motion of the substance

The U-value of a structure is the amount of heat energy conducted per second through 1 m² of that structure when a temperature difference of 1 °C (1 K) is maintained between its ends

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*How well part of a building conducts heat
*Bad insulators (good conductors) have high U-value

the transfer of heat energy from one place to another in the form of electromagnetic waves

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*Darker: more radiation
*Shiny: less radiation (I think)

The average amount of the Sun's energy falling per second perpendicularly on 1 m² of the Earth's atmosphere is the solar constant. Its value is about 1.35 kW m⁻²

Solar Panels

Tubes to heat water p172 fig 15.12

Convection is the transfer of heat through a fluid by means of circulating currents of fluid caused by the heat

A disturbance that carries energy from one place to another

A travelling wave, either electromagnetic or mechanical, is a disturbance that travels out from the source producing it, transferring Energy from the source to other places through which it travels

A disturbance carrying energy through a medium without any overall motion of that medium

Energy transmitted from one place to another at the speed of light (3×10⁸ ms -¹ in a vacuum)

The frequency of a wave is the number of cycles passing per second

A wave where the direction of vibration is parallel to the direction in which the wave travels

A wave where the direction of vibration is perpendicular to the direction in which the wave travels

❌ How high the wave is

❌ Distance between 2 corresponding points on a wave

The bouncing of waves off of an obstacle in their path

The changing direction of a wave when it enters a region where its speed changes

The spreading out of a wave when it passes through a gap or passes by an obstacle

When waves from two sources meet, they combine to form a new wave.

The displacement at any point on the new wave is the algebraic sum of the displacements of the two original waves.

This is interference of waves.

When waves from two sources meet they combine to form a new wave.

If the amplitude of the new wave is greater than the amplitudes of each of the individual waves, the waves are said to undergo constructive interference.

When waves from two sources meet they combine to form a new wave.

If the amplitude of the new wave is less than the amplitudes of each of the individual waves, the waves are said to undergo destructive interference.

Two sources are coherent if the waves from each source are in phase or have a constant phase difference between them.

If this is so they must also have the same frequency.

If the vibrations of a transverse wave are confined to one plane only, that wave is said to be polarised.

When two periodic travelling waves of the same frequency and amplitude moving in opposite directions meet, they interfere with each other.

The resulting wave formed is called a stationary wave, or a standing wave.

The apparent change in the frequency of waves due to the relative motion of the source and the observer

❓ The frequency of vibration of every vibrating particle on a stationary wave is the same.

The frequency or a stationary wave is the same as the frequency of the travelling wave producing it.

Frequencies which are multiples of a certain frequency are called overtones of that frequency

The loudness of a note depends on the amplitude of the sound wave. The greater the amplitude the greater the loudness

The pitch of a note depends on the frequency of the sound wave. The higher the frequency, the higher the pitch

The quality of a musical note depends on the number of overtones present in the note and the relative strengths of the different overtones present

The highest and lowest frequencies that can be heard by a normal human ear. The range is 20 HZ - 20,000 HZ

The transfer of energy between 2 bodies of the same natural frequency

The rate at which sound energy is passing through unit area at right angles to the direction in which the sound is travelling at that point

The smallest sound intensity detectable by the average human ear at a frequency of 1 kHz. Its value is 1 × 10⁻¹² W m⁻²

Sound intensity level is measured in decibels (dB)

A string vibrating with an antinode at it's centre and a node at each end (and no other nodes or antinodes) is vibrating at its fundamental frequency

Frequencies which are multiples of a certain frequency f are called harmonics.
f is called the fundamental frequency or the first harmonic. 2f is the second harmonic, 3f is the third harmonic, etc.

• Person on a spring being pushed every time they move away
• Barton's pendulumns (LEARN)
• Glasses shattering with high pitched notes
• Column of air in a tube resonating with a tuning fork
• Buildings in an earthquake

*When the sound intensity (in W m⁻²) doubles, sound intensity level increases by 3 dB.

All harmonics

Odd numbered harmonics only

Learn about it

*mass per unit length

Ok?

Learn it

• Heavy base
• Turntable
• Collimator
• Astronomical Telescope

• Cross-threads in focus
• Distant object appears in focus
• Slit is in focus
• Width of the slit
• Level the turntable

Diffraction or interference

Red - 7 × 10⁻⁷ m
Orange
Yellow - 6 × 10⁻⁷ m
Green
Blue - 5 × 10⁻⁷ m
Indigo
Violet - 4 × 10⁻⁷ m

The distance d between two adjacent slits (i.e. the width of one line and one slit) on the grating

d = [1 ÷ (n × 1000)] metres

Proof

™ Constructive interference will occur at angle θ if |AB| is a whole number of wavelengths.
i.e. |AB| = nλ where n = 1, 2, 3, etc.

Polarisation

Polarisation is a property of certain types of waves that describes the orientation of their oscillations

The separating out of the different wavelengths (colours) present in light

Primary: Red, Green, Blue
R+G: Yellow
R+B: Magenta
G+B: Cyan

When two primary colours are mixed in equal intensity, the colour formed is a secondary colour

A primary colour and the secondary colour that when mixed give white are called complementary colours

Prism: Violet the most
Grating: Red the most

Gamma ray - 0.01 nm
X - Ray - 1 nm
UV - 0.1 μm
Visible Light - 0.4-0.7 μm
Infrared - 0.01 mm
Microwaves - 1cm
TV & Radio: 1m - 1km