Wave Properties and SI Units

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Questions and Answers

What does the unit Hz specifically measure?

Speed of a wave

Distance travelled by a wave

Number of cycles per second (correct)

Time taken for one complete oscillation

What is the formula relating wave speed, frequency, and wavelength?

v = f - λ

v = f + λ

v = f × λ (correct)

v = λ / f

Which of the following describes longitudinal waves?

Particles remain stationary

Particles move parallel to the direction of wave travel (correct)

Particles move in a circular motion

Particles move perpendicular to the direction of wave travel

Which is NOT a behavior of waves?

Dissipation Signup and view all the answers

What is the relationship between time period (T) and frequency (f)?

T = 1 / f Signup and view all the answers

How is the speed of sound generally measured?

By using two microphones to measure time Signup and view all the answers

What is meant by the term amplitude in the context of waves?

The maximum displacement of particles from their rest position Signup and view all the answers

What frequency range can humans hear?

20 Hz to 20,000 Hz Signup and view all the answers

What does the X-axis on a Cathode Ray Oscilloscope (CRO) represent?

Time represented in milliseconds or microseconds Signup and view all the answers

How is the amplitude of a waveform on a CRO determined?

By counting vertical divisions from the baseline to the peak or trough Signup and view all the answers

What happens when you adjust the time base knob to a larger value on the CRO?

Slower signals are displayed Signup and view all the answers

What is the relationship between frequency (f) and time period (T)?

f = 1 / T Signup and view all the answers

When measuring wavelength on a CRO, what should you do?

Count the horizontal divisions between two peaks and multiply by the time base Signup and view all the answers

Which knob would you use to compress or stretch the waveform vertically on the CRO?

Volts/Div knob Signup and view all the answers

What does the trigger function do on a CRO?

It helps synchronize the waveform display for stability Signup and view all the answers

If the gain is set to 5 mV/div and the wave spans 3 divisions, what is the amplitude?

15 mV Signup and view all the answers

How do you calculate the frequency of a wave if the time period is measured as 4 ms?

f = 1 / 0.004 s = 250 Hz Signup and view all the answers

In terms of wave properties, what does diffraction refer to?

Waves bending around obstacles Signup and view all the answers

What prefix represents one million in wave measurements?

mega Signup and view all the answers

Which of the following statements about reading a CRO is true?

The waveform must be stable to gather accurate readings. Signup and view all the answers

What is indicated by the vertical divisions on a CRO?

Voltage of the signal Signup and view all the answers

What is the typical function of the cursor feature on modern oscilloscopes?

To calculate values directly on the screen Signup and view all the answers

If the wave period spans 6 divisions and the time base is set to 1 ms/div, what is the time period?

6 ms Signup and view all the answers

Study Notes

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

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Description

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.