A Level Physics: progressive, longitudinal and transverse waves

Physics A Level Revision

• Topic 1 - Measurements and Errors
• Topic 2 - Particles and Radiation
• Topic 3 - Waves and Optics
• Topic 4 - Mechanics and Materials
• Topic 5 - Current Electricity
• Topic 6 - Further Mechanics
• Topic 7 - Fields and Consequences
• Topic 8 - Nuclear Physics

Topic 3 - Waves and Optics

• Progression Waves
• Longitudinal and Transverse Waves
• Superposition and Standing Waves
• Young's Slit and Interference
• Diffraction

Progression Waves

• A wave can be described as progressive if it moves outwards from the source

Longitudinal and Transverse Waves

• All waves are called by oscillations and all transfer energy without transferring matter
• Longitudinal Waves - a wave in which the displacement of particles is parallel to the direction of energy transfer
• when the particles are close together, we call it a compression and when they are spread out, we call it a rarefaction
• the wavelength is the distance from one compression to the next
• the amplitude is the maximum distance the particles move from its equilibrium position right or left
• sound waves / seismic P - waves
• Transverse Waves - a wave in which the displacement of particles is perpendicular to the direction of energy
• the wavelength is the distance from one peak to the next
• the amplitude is the maximum distance the particles moves from its equilibrium position up or down
• water waves / electromagnetic waves / seismic S - waves

Polarisation

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• Caption: Diagram showing polarisation
• Polarisation restricts the oscillations of a wave to one plane - in the diagrams the light is initially oscillating in all directions
• A piece of Polaroid only allows light too oscillate in the same direction as it
• in the top diagram, the light passes through a vertical plane and becomes polarised in the vertical plane so it can pass through the second Polaroid
• in the middle diagram, the light becomes polarised in the horizontal plane
• In the bottom diagram, the light becomes vertically polarised but this cannot pass through a horizontal plane Polaroid

Superposition and Standing Waves

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• Caption: Three examples of the resultant waves: an amplitude of 1.5 , no resultant wave and amplitude of 2.0
• Superposition - the process by which two waves combine into a single wave form when they overlap
• Stationary Waves - when two similar waves travel in opposite directions, they can superpose to form a stationary wave ; these then form nodes and antinodes
• Nodes - positions on a standing wave which do not vibrate as the waves combine to give zero displacement
• Antinodes - positions of a standing wave where there is a maximum displacement
• Harmonics
• First harmonic - 2 nodes and 1 antinode
• Second harmonic - 3 nodes and 2 antinodes
• Third harmonic - 4 nodes and 3 anitnodes

Diffraction

• Interference - when two waves of the same type occupy the same space
• The two overlapping waves must be coherent
• the same frequency
• a constant phase difference
• Diffraction - spreading out of bending of waves as they pass through a gap or around an obstacle
• diffraction is greatest when the wavelength when the wavelength is approximately the same as the width of the gap
• SINGLE SLIT DIFFRACTION
• when light passes through a narrow slit, a pattern of alternate bright and dark fringes is produced
• this is called a single slit diffraction pattern

Comparing Progressive and Stationary

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• Caption: Comparing the two types of waves

Topic 4 - Mechanics and Materials

• MATERIALS
• Springs
• Hooke's Law
• Young Modulus
• MECHANICS
• Vectors
• Moments
• Momentum
• Projectiles
• Newton's Laws

Springs

• Hooke's Law - The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length; so there is the equation F = ke
• Where F = force k = spring constant e = extension of the wire
• Spring Constant - this tells use the stiffness of a material
• a small force causes a large extension the spring constant will be small - very stretchy
• a large force causes a small extension the spring constant will be large - not stretchy
• Springs in Series

Topic 5 - Electricity

• Current and Potential Difference
• Resistance and Ohm's Law
• Resistance and Superconductors
• Resistivity
• EMF and Internal Resistance
• Capacitors

Current and Potential Difference

• Current - Electrical current is the rate of flow of charge in a circuit / the rate of flow of electrons
• Potential Difference - the work done per unit charge / energy given to each electron or the pushing force of the electrons
• Resistance - How easy or difficult it is to make a current flow through a material

Resistance and Ohm's Law

• For something to obey Hooke's Law the current flowing is proportional to the potential difference pushing it
• Taking Measurements
• To measure the potential difference, we use a voltmeter connected in parallel
• To measure the current, we use an ammeter connected in series
• I - B Graphs