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Wave: A succession of pulses.

Rest position: The equilibrium position of the medium before a pulse/wave is generated.

Oscillation: one complete swing or vibration.

Transverse pulse/wave : a pulse/wave that moves in a direction perpendicular to the direction of the disturbance in a medium.

Wavelength: the distance between two consecutive points on the wave that are in phase.

Amplitude: the maximum displacement of a particle from its rest (equilibrium)
position.

Period: the time taken for a wave to pass a point. The symbol for period is T, and its unit is second (s).

Frequency: the number of waves passing a point in one second. The symbol for frequency is f, and its SI unit is hertz (Hz).

Wave speed: the product of frequency and wavelength of a wave.

Longitudinal pulse/wave: a pulse/wave that moves in the same direction as the
disturbance in the medium.

Compression: a point on a medium through which a longitudinal wave is traveling that has the particles of the medium closely packed.

Rarefaction: a point on a medium through which a longitudinal wave is traveling that has the particles of the medium spaced apart.

Principle of superposition: States that when two disturbances occupy the same space at the same time, the resulting disturbance is the sum of two disturbances.

Photon: the smallest particle of light, which has no mass and which carries energy. (it behaves like both a wave and a particle)

The Law of Reflection:
1. The incident ray, the reflected ray and the normal all lie in the same plane.
2. The angle of incidence is equal to the angle of reflection.

Refraction: the change in direction of a wave when passing from one medium to
another due to the change in speed.

Optical density: the measure of the ease with which a material transmits light.

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Wave = A succession of pulses.

Pulse = A single disturbance traveling through a medium.

Medium = A substance or material through which a wave moves.

DEMO WITH A SLINKY.

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Transverse waves and Longitudinal waves:

Transverse wave - The disturbance that makes up the wave, where the particles disturbed by the wave move perpendicular to the direction of the wave. (e.g. Light, EM radiation, Water waves)

Longitudinal wave - The disturbance that makes up the wave where the particles disturbed by the wave move parallel to the direction of the wave (e.g. Sound). Known as a PRESSURE WAVE.

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Perpendicular motion of particles relative to direction of wave creates transverse waves. 

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Perpendicular motion of particles relative to direction of wave creates transverse waves. 

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Movement of particles in a transverse wave

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Movement of particles in a transverse wave

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Energy flow through the wave, not matter. 

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Energy flow through the wave, not matter. 

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Flow of energy not matter in transverse waves

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Predicting the position of a particle in a transverse wave in the next time interval, as the wave moves through the medium:

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Predicting the position of a particle in a transverse wave in the next time interval, as the wave moves through the medium:

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Does the particle move UP or DOWN next?

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v = f. λ                        where, v is speed
f is frequency
λ is wavelength

HOW TO DERIVE THE WAVE EQUATION:
We know:                speed = distance / time
For a wave:             speed = wavelength / time
= λ / T
= λ x 1/T
= λ x f
v = fλ

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GCSE Physics Revision: The wave equation

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v = f λ

Page | 8
Example 3:
Waves with a frequency of 0,9 Hz are produced by a long rope. The wavelength of
the wave is 1,5 m. Calculate the speed of the wave.

Example 4:
The period of the waves produced by the spring is 0,5 seconds. The speed of the
wave is 6 m.s-1

4.1 What is the frequency of the waves?

4.2 Calculate the wavelength of the waves.

Page | 9
Example 5:
The slinky spring produces waves with a frequency of 3Hz and wavelength of 60cm.

5.1 Calculate the speed of the waves.

5.2 What will the wavelength be if the frequency is increased to 9 Hz?

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Theory page 6 - Make correction to amplitude on wave

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Superposition causing constructive or destructive interference.  

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Superposition causing constructive or destructive interference.  

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Interference of Waves | Superposition and Interference in light and water waves | Physics

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1. Define a longitudinal wave.

2. Draw a labelled diagram of a longitudinal wave.

3. A longitudinal wave travelling at 340 m.s-1 in air has a wavelength of 2,1m

3.1 What is meant by the term ‘wavelength’ with regard to a longitudinal
wave?

3.2 Calculate the frequency of the wave.

3.3 Calculate how far a compression will travel in one minute.

4. A certain wave has a frequency of 1900 Hz and wavelength of 18 cm.
Calculate the speed of the wave.

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With Memo - old hard copy notes (work through what you can)

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Sound waves are pressure waves.

Pressure is force per unit area.

Hence, sound causes matter to vibrate.

Illustrated in video below:

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CYMATICS: Science Vs. Music - Nigel Stanford

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Sound is a pressure wave:

it needs a MEDIUM to propogate through

it cannot travel through a vacuum

it contains compressions (compressed areas)

it contains rarefactions (stretched out areas)

it's speed is 343 m.s⁻¹ (in dry air at room temperature 20 degrees C)

NOTE:

We DRAW longitudinal waves using VERTICAL LINES:

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Sound travels at:

331 m/s in air at 0 degrees C

343 m/s in air at room temperature

1 480 m/s in water (4.3 times as fast as in air)

5 120 m/s in iron (about 15 times as fast as in air)

12 000 m/s in exceptionally stiff material such as diamond (about 35 times as fast as in air) - maximum speed that sound will travel under normal conditions

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Sound waves need a medium to travel through 

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Sound waves need a medium to travel through 

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Sound waves presented on an oscilloscope

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Sound waves presented on an oscilloscope

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An oscilloscope is a device that simply converts a sound wave (which is a longitudinal wave) into a transverse wave, for the purpose of making sound "visible".

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Ampulitude of sound wave = Loudness
Frequency of sound wave = Pitch

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Sound wave conversion on an Oscilloscope 

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Sound wave conversion on an Oscilloscope 

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Compressions translate to crests.

Rarefactions translate to troughs.

The louder a sound, the greater the amplitude of the wave.

The higher the pitch (“lowness our highness”) of the sound, the greater the frequency of the wave, i.e. waves get more squashed together.

NOTE:

SOUND WAVES = LONGITUDINAL WAVES (NOT TRANSVERSE WAVES!!)

An oscilloscope is an instrument that converts sound waves into electrical signals to show how the amplitude of sound waves changes with time.

An oscilloscope displays any longitudinal wave as a transverse wave.
•oscilloscope display: voltage – time
•microphone diaphragm vibrates, producing an a.c. waveform

Sound waves ARE NOT TRANSVERSE WAVES!

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For humans: from 20 Hz to 20000 Hz

Elephant: 16 Hz to 12,000 Hz

Cow: 16 Hz to 40,00 Hz

Cat: 100 Hz to 32000 Hz

Dog: 40 Hz to 46000 Hz

Rabbit: 1000 Hz to 1,00,000 Hz

ULTRASOUND = Sound with frequency > 20 000 Hz

INFRASOUND = Sound with frequency < 20 Hz

Ultra- and infrasound are inaudible, as they fall out of our audible hearing range.

Terms used for how fast an object MOVES:

HYPERSONIC = speed of object ≥ Mach 5

SUPERSONIC = Mach 1 < speed of object < Mach 5

SUBSONIC = speed of object < Mach 1 (v sound at spec. temperature)

NOTE: Mach 1 = 343 m.s⁻¹

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Noise = irregular and non-repeating pattern

Non-noise (musical instruments, singing, periodic speech voice) = regular and repeating pattern

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Example 1:
The frequency of a wave is 20 Hz. Calculate its period.

Example 2:
The period of water waves is 12,5 seconds. What is its frequency?Period = the time taken for one complete wave to pass a fixed point.
Symbol for period = T
Unit = s (for seconds)

Frequency = the number of waves passing a given point in 1 second.
Symbol in equation = f
Unit = Hz (Hertz, s⁻¹ as in “per second”)

Frequency and period are inverses of each other.
Therefore,                                 f = 1/T
and,                                           T = 1/f

NOTES: p. 7
Example 1:
The frequency of a wave is 20 Hz. Calculate its period.

Example 2:
The period of water waves is 12,5 seconds. What is its frequency?

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Resonance is:
The increase in amplitude of oscillation of an electric or mechanical system exposed to a periodic force whose frequency is equal or very close to the natural frequency of the system.

Resonance is responsible for:

A glass breaking when you sing at it at its natural frequency

A bridge collapsing when wind blows over it and through the cables at the same frequency as the bridge's or cables’ natural frequency

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Why Physics Is Awesome:  The Power Of Resonance!

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When moving at v > vsound, the sound barrier is broken.

Jet speed > 1200km/h, you will hear a sonic boom

Mach 1 = 343 m/s = v sound

Mach 2 = 686 m/s = 2v sound

Mach number = the ratio of air speed to local speed of sound.

At altitude, Mach number is a function of temperature.

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ARMY Plane BREAKS Sound Barrier - Creating a Sonic Boom

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A sonic boom = a shock wave created by an object that travels faster than the speed of sound through air.

A sonic boom generates enormous amounts of sound energy

A sonic boom sounds like an explosion

If supersonic moving aircraft fly too close to buildings, it can break windows

If a person is exposed to a loud enough sonic boom, it could cause death (sonic boom can cause an embolism in the lungs which then travels to the heart)

The sound of the boom is heard before the sound of the plane

Sonic booms from the Falcon Heavy launch rocket boosters re-entry:

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The Incredible Sounds of the Falcon Heavy Launch (BINAURAL AUDIO IMMERSION) - Smarter Every Day 189

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Sonic Boom Explained - How is it Created - Animated Graphics

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Why is ultrasound used in sonar? | #aumsum #kids #science #education #children

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When the Bleep Are We Going to Use That!

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Wave Barrier Reflections and the Echo Formula

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Physics Lesson - Echo Problem & using Temperature to find Speed of Sound

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f = 1/T
and
T = 1/f                                 where, T is the period of a wave measured in second (s)
f is the frequency of a wave in hertz (Hz)

v = f λ                                  where, v is the speed of the wave in m.s⁻¹ and λ is the wavelength in m.

c = f λ                                  where, c is the speed of light = 3 x 10⁸ m.s−1
f is the frequency measured in hertz (Hz)
λ is wavelength measured in metres (m)

n = c/v                                 where, n is the refractive index (no units)
c is the speed of light in a vacuum in m.s⁻¹
v is the speed of light in medium in m.s⁻¹

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LIGHT = ELECTROMAGNETIC WAVES
Consists of 2 perpendicular waves:

a vertical electric field and

a horizontal magnetic field,

in phase with each other.

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Radiation of all frequencies travels at the same velocity through space. The speed of light in vacuum, c, is equal to 3 x 10⁸ m.s−1.

The wavelength and frequency of these waves can be calculated using the wave equation,

c = f λ

where c is the speed of light = 3 x 10⁸ m.s−1
f is the frequency measured in hertz (Hz)
λ is wavelength measured in metres (m)

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Waves can be:

1. Reflected

2. Refracted

3. Diffracted

4. Superimposed (interference)

Descriptions:

Reflection of waves is the bouncing of waves off straight barriers; it follows the law of reflection.

Refraction is the change in direction of waves that occurs when waves travel from one medium to another. Refraction is always accompanied by a wavelength change and speed change.

Diffraction is the bending of waves around obstacles and openings.

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Light & Optics: "The Nature of Light" 1948 Coronet Instructional Films; Reflection, Refraction...

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(c) Extinction of the waves are achieved.
Principle applied in Polaroid sun glasses.

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REFRACTION: Light changes direction in a different density medium

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REFRACTION: Light changes direction in a different density medium

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A light wave consists of individual photons which act as individual wave fronts, slowing down at the rate it enters the different medium.

This changes the direction of the light path.

From less dense to more dense media, the light path bends TOWARDS NORMAL LINE.

From more dense to less dense media, the light path bends AWAY FROM NORMAL LINE.

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What characteristic of light explains why an inverted image of an object forms in a pinhole camera?

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Wave-Particle Duality Explained with Double Slit Experiments | CHRISTMAS LECTURES1999 | Neil Johnson

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Albert Einstein and The Photoelectric Effect | AMS OpenMind

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When light passes from a less dense to a more dense substance, (for example passing from air into water), the light is refracted (or bent) towards the normal. The normal is a line perpendicular (forming a 90 degree angle) to the boundary between the two substances. ... As the light enters the water, it is refracted.

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REFLECTION

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REFRACTION LAB PRAC - Law of Refraction (Snell’s Law)

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REFRACTION LAB PRAC - Law of Refraction (Snell’s Law)

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Procedure:
1. Use a protractor to measure the angle of incidence (between ray and Normal line) and angle of refraction in each instance below:

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2. Place the block on the sheet of paper and direct a ray streak onto the slit. Observe the ray tracks and measure the angles.

3. Change the angle with which the ray strikes the flat face, and record the angles of incidence and refraction again.

4. Repeat the process to collect a range of angles from zero,then 10 through 80 degrees.

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1. State the mathematical relationship emerging from this graph.

2. Do you think that water will refract light rays less or more than the Perspex block? Explain your answer.

3. Will the refractive index (n) of water be larger or smaller than n of the perspex block?

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5. Tabulate your results.

6. Calculate values of sin i/sin r for each pair of readings. Tabulate this in an extra column in your table.

7. Plot a graph of sin i against sin r. That is sin i on the y-axis and sin r on the x-axis.

8. Calculate the gradient of the graph. The value of the gradient of your graph is the refractive index.

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A Level Physics - Refraction and Snell's Law

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Index of refraction of a medium is a measure of how dense it is.
Index of refraction = n = c / v light in the medium

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sin(i)/sin(r) = n
= n refractive medium/n air
NOTE: n air = 1
n air sin(i) = n refractive medium sin(r)

n ₁ sin(i) = n ₂ sin(r)                               This is SNELL’S LAW

Also: n = c/v
= speed of light in a vacuum/ speed of light in different medium

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How to Solve a Snell's Law Problem (angle of refraction)

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Why is light slower in glass? - Sixty Symbols

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Real vs apparent depth

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Boats and boating--Equipment and supplies

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n 1 sinθ ₁ = n 2 sinθ 2                             where 1 = the incident medium
2 = the refracting medium

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TOTAL INTERNAL REFLECTION AND CRITICAL ANGLE

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TOTAL INTERNAL REFLECTION AND CRITICAL ANGLE

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TOTAL INTERNAL REFLECTION = the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.

CRITICAL ANGLE = the size of an incident angle that produces a refracted angle of 90°.

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Total Internal Reflection Demo: Optical Fibers

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OLD NOTES

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Refractive index = the ratio of the speed of light in a vacuum to its speed in a refractive       material, where bending of a ray of light occurs when passing from a medium into another with different density.

Optical density = a measure of the refracting power of a medium.

T.O.T. = the complete reflection of a light ray reaching an interface with a less dense medium, when the angle of incidence exceeds the critical angle.

Critical angle = The angle of incidence where the angle of refraction is 90°.

Normal = the line that is perpendicular to the plane of the surface.

c = 299 792 458 m.s⁻¹ ≃ 3 x 10 8 m.s⁻¹