Wave Properties and SI Units

SI Units

• Hertz (Hz): Unit of frequency, cycles per second
• Meters (m): Unit of distance, wavelength
• Seconds (s): Unit of time
• Meters per second (m/s): Unit of speed, wave speed

Terminology and Definitions

• Oscillations: Repeated back-and-forth motion
• Vibrations: Rapid particle movements in a medium
• Frequency: Number of oscillations per second (Hz)
• Wavelength: Distance between consecutive crests/troughs
• Speed: Wave travel rate (m/s)
• Energy Propagation: Movement of energy as waves through a medium
• Medium: Material through which a wave travels (e.g., air, water)
• Amplitude: Maximum displacement of particles from rest, related to wave height
• Time Period: Time for one complete oscillation (s)

Wave Types

Transverse Waves

• Particle motion: Perpendicular to energy propagation (e.g., up and down)
• Examples: Light, water, string waves

Longitudinal Waves

• Particle motion: Parallel to energy propagation (e.g., back and forth)
• Examples: Sound, shock, pressure waves

Wave Equation

• Wave speed (v) = Frequency (f) × Wavelength (λ)
• Formula: v = fλ

Time Period/Frequency

• Time period (T): Time for one oscillation
  • Formula: T = 1/f
• Frequency (f): Oscillations per second
  • Formula: f = 1/T

Wave Behavior

• Reflection: Wave bouncing off a surface
• Refraction: Wave changing direction due to speed change in a new medium
• Diffraction: Wave spreading around obstacles or through gaps

Sound

• Production/Transmission: Sound produced by vibrating objects, travels through a medium
• Speed of Sound: Speed = Distance/Time
• Practical measure: Use two microphones to measure sound speed.
• Human Hearing Range: 20 Hz to 20,000 Hz
• Noise: Unwanted or unpleasant sound

Cathode Ray Oscilloscope (CRO)

• Measuring Time Period: Use time base setting to measure time for one complete oscillation
• Calculating Frequency: f = 1/T
• Waveform Display: Shows waveforms of sound sources (e.g., music)

Ripple Tank Waves

• Reflection: Waves bouncing off barriers
• Refraction: Waves changing direction in different media
• Diffraction: Waves spreading around objects or through gaps

Reading a CRO

Understanding the Display

• Horizontal axis (X-axis): Time (ms or µs/div)
• Vertical axis (Y-axis): Voltage (V/div)

Adjusting Time Base & Voltage

• Time base (Time/Div knob): Controls how fast signal moves; higher = faster; lower = slower
• Voltage scale (Volts/Div knob): Controls signal height; higher = compressed; lower = stretched

Reading the Signal

• Frequency: Calculate from time period. (f = 1/T) Example: 2 ms /Cycle --> 500 Hz.
• Amplitude: Vertical distance from baseline to peak/trough. Example: 4 divisions x 2V/division --> 8V
• Wavelength: Horizontal distance between peaks/troughs.

Using Cursors

• Modern CROs have cursor functions to provide direct measurements.

Triggering

• Trigger function: Synchronizes waveform display – adjust trigger level and slope to get a stable waveform.

Summary of Formulas and Concepts

• Time Period (T): Horizontal length of one cycle
• Frequency (f): 1 / Time Period (T)
• Amplitude: Vertical distance from baseline to peak/trough
• Wavelength: Measured along the X-axis for one full cycle.
• Wave speed (v): f x λ
• Time Period/Frequency formulas (T = 1/f and f = 1/T)

Determining Wave Characteristics from a CRO

• Amplitude:

  • Look at the vertical scale (Y-axis), which shows mV/div or V/div.
  • Count the vertical divisions from baseline to peak (or trough).
  • Multiply the number of divisions by the gain to get the amplitude. (Amplitude = divisions x gain in mV/div or V/div)

• Time Period:

  • Check horizontal scale (X-axis) with either ms/div or s/div marking.
  • Count the horizontal divisions from one peak to the next peak (or trough to trough) representing one cycle.
  • Calculate the time period: (Time Period = divisions x time base in ms/div or s/div)

• Frequency:

  • Calculate from knowing the time period: (f = 1 / Time Period).

Standard Prefixes

• Prefixes to express very large or small numbers (important for GCSE):
  • nano (n): 10^-9
  • micro (µ): 10^-6
  • milli (m): 10^-3
  • kilo (k): 10³
  • mega (M): 10⁶
  • giga (G): 10⁹

Explore the fundamental concepts of wave properties and SI units in this quiz. You'll learn about frequency, wavelength, and the types of waves including transverse and longitudinal. Test your understanding of key terminology and definitions related to waves.