Topic C Definitions

Definitions for Topic C1-C5 (only 4,5 ratings), bold are most important parts of definition, missing extra notes in parts, SL & HL definitions

Amplitude

Maximum displacement from the equilibrium position

Simple harmonic motion (SHM)

Oscillatory motion in which the acceleration is proportional to displacement from the equilibrium position and in the opposite direction to the displacement

Frequency (f)

Number of oscillations per unit time

Longitudinal wave

Wave in which oscillations of particles are parallel to direction of energy transfer

Properties that are common to all electromagnetic waves

transverse; do not need a medium/can travel through a vacuum; can be polarized (not in syllabus but can still get credit); all have same speed in a vacuum

Transverse wave

A wave where the oscillation of particles in perpendicular to the direction of energy transfer

Electromagnetic waves

Transverse waves moving at the speed of light in vacuum consisting of oscillating electric and magnetic fields at right angles to eachother

Mechanical wave

Wave which requires a medium (e.g. sound)

Can be longitudinal or transverse (unlike EM waves)

White light diffraction pattern explanation

White central maximum - central maxima of all wavelength coincide

Coloured fringes with blue end of spectrum closer to centre - shorter wavelength will mean first minimum will occur at smaller angle/destructive interference occurs with smaller path difference

Single slit diffraction pattern

Central maximum twice width of other maxima

Other maxima < 5% intensity of central

Principle of Superposition

When two waves meet, the resultant displacement is the vector sum of the displacements of the component waves

Coherence

Coherent sources have constant phase difference

Refractive index (index of refraction) (n)

The ratio of the speed of light in a vacuum to the speed of light in the material (ratio of sine of angle of incidence in a vacuum to sine of angle of refraction)

Description of double-slit diffraction pattern

Constant separation of maxima, constant intensity of maxima (true for “zero” width slits

Explanation of double slit diffraction pattern

• Waves from two sources interfere/superpose

• If path difference is an integer multiple of wavelength they arrive in phase → constructive interference → maximum

• If path difference is an odd multiple of half-wavelength they arrive out of phase → destructive interference → minimum

Refraction

Refraction caused by change in speed and wavelength changes proportionally to speed, frequency doesn’t change with refraction

Monochromatic

Waves all have the same frequency/wavelength

Ray

Line:

• Indicating the direction of motion of the energy transfer

• Perpendicular to a wavefront

Wavefront

Line joining points on a wave that are in phase with eachother

Critical angle

The angle of incidence for which the angle of refraction is 90 degrees (OR the incident angle above which total internal reflection occurs)

Snell’s Law

The rato of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for a given frequency

Total internal reflection

When the angle of incidence is greater than the critical angle, the incident ray only reflects with no refracted ray

The phase of a wave increases by pi (radians)…

upon reflection from a slower medium or a fixed/closed end

Young’s double slit experiment

Double slit experiment with light

When not using a laser (which is a coherent source) need a single slit in front of the double slit to give a coherent source for the light

Changes to diffraction pattern with multiple slits

As number of slits increase:

• Primary maxima become brighter/more intense (proportional to n²)

• Primary maxima become narrower

• Secondary maxima increase in number (n-2 subsidiary maxima)

• Secondary maxima decrease in intensity

Limit is diffraction grating: very narrow, intense primary maxima; secondary maxima disappear altogether.

Diffraction

The spreading of a wave past an aperture or an obstacle

Critical damping

When a resistive force is applied to an oscillating system that causes the particle to return to static equilibrium in the smallest possible time

Formation of standing waves

(usually) wave interferes with its own reflection

Standing wave

A wave formed from the superposition of two identical travelling waves moving in opposite directions

Standing wave/travelling wave differences

No energy propagated in a standing wave, energy propagated in travelling wave;

The amplitude of a standing wave is not constant, amplitude of travelling wave constant;

Points along a standing wave are either in phase or 180 deg out of phase with eachother, points on travelling wave less than a wavelength apart all out of phase with eachother

Damping

The loss of energy in an oscillating system

Involves a force that is always in the opposite direction to the direction of motion of the oscillating particle

Antinode

Locations of maximum constructive interference on a standing wave

Node

Location of constant complete destructive interference on a standing wave

First harmonic

The lowest frequency mode of a standing wave

Resonance

A transfer of energy in which a system is subject to an oscillating force that matches the natural frequency of the system resulting in a large amplitude of vibration

Origin of doppler effect

Moving source: wavelength decreases/increases; speed same; so apparent frequencey increases/decreases

Moving observer: Wave speed increases/decreases; wavelength same; so apparent frequency increases/decreases

(Both versions helped by diagrams)

Doppler effect

The change in measured/apparent frequency when there is relative motionbetween source and observer

Blueshift

A decrease in the observed wavelength of electromagnetic radiation due to relative motion

Redshift (as a phenomenon)

An increase in the observed wavelength of electromagnetic radiation due to relative motion