Comprehensive N5 Physics Waves and Electromagnetic Spectrum Study Guide

Prefixes and Scientific Notation

• Metric Prefixes and Multipliers:

  • Giga: $\times 10^9$

  • Mega: $\times 10^6$

  • Kilo: $\times 10^3$

  • milli: $\times 10^{-3}$

  • micro: $\times 10^{-6}$ (Note: Font styling can vary for the micro prefix symbol; if a prefix symbol is ambiguous or hard to read, it represents micro)

  • nano ($n$): $\times 10^{-9}$

Fundamental Wave Equations

• Distance, Speed, and Time Relationship:

  • Equation: $d = vt$

  • $d$: Distance, measured in metres ($\text{m}$)

  • $v$: Speed, measured in metres per second ($\text{ms}^{-1}$

  • $t$: Time, measured in seconds ($\text{s}$

• Wave Speed, Frequency, and Wavelength Relationship:

  • Equation: v = f\nlambda

  • $v$: Speed, measured in metres per second ($\text{ms}^{-1}$

  • $f$: Frequency, measured in hertz ($\text{Hz}$

  • $\lambda$: Wavelength, measured in metres ($\text{m}$

• Frequency Equation:

  • Equation: $f = \frac{N}{t}$

  • $f$: Frequency, measured in hertz ($\text{Hz}$

  • $N$: Number of waves (no unit / dimensionless)

  • $t$: Time, measured in seconds ($\text{s}$

• Period Equation:

  • Equation: $T = \frac{1}{f}$

  • $T$: Period, measured in seconds ($\text{s}$

  • $f$: Frequency, measured in hertz ($\text{Hz}$

Wave Classification and Definitions

• Energy Transfer:

  • As waves travel, they transfer ENERGY.

• Transverse Waves:

  • Definition: A wave that causes the particles of the medium to vibrate at right angles ($90^\circ$) to the wave's direction of travel.

  • Electromagnetic Waves: All waves on the Electromagnetic (EM) spectrum are transverse waves.

  • General Classification: At N5 level, all waves other than sound are transverse waves.

• Longitudinal Waves:

  • Definition: A wave that causes the particles of the medium to vibrate parallel to the wave's direction of travel.

  • Example: Sound is an example of a longitudinal wave (at N5 level, sound is the only longitudinal wave considered).

• Key Wave Terminology:

  • Frequency: The number of waves per second.

  • Period: The time taken for one complete wave to pass a point.

Calculation Examples

• Wavelength Calculation Example:

  • Given Parameters: Total length = $10\,\text{m}$; Number of complete waves in $10\,\text{m}$ = $2.5$

  • Formula: $\text{Wavelength} = \frac{\text{Total Length}}{\text{Number of Waves}}$

  • Calculation: $\text{Wavelength} = \frac{10\,\text{m}}{2.5} = 4\,\text{m}$

• Amplitude Calculation Example:

  • Given Parameters: Total height from peak to trough = $4\,\text{m}$

  • Calculation: $\text{Amplitude} = \frac{4\,\text{m}}{2} = 2\,\text{m}$

Wave Behaviors: Diffraction

• Definition of Diffraction:

  • Diffraction is when waves "bend" around an obstacle or through a gap.

• Factors Affecting Diffraction:

  • Frequency and Wavelength Relationship: Increasing the frequency of light decreases its wavelength.

  • Gap Size Effect:

  • Smaller gap size produces MORE diffraction.

  • Larger gap size produces LESS diffraction (waves pass through with minimal bending at the edges).

  • Wavelength Effect:

  • Larger wavelength produces MORE diffraction.

  • Frequency Effect:

  • Smaller frequency produces MORE diffraction (because lower frequency corresponds to larger wavelength).

• Driving Through Hills Scenario:

  • Problem: When driving through hills listening to the radio, a driver receives a good signal on Station A but a poor signal on Station B.

  • Explanation: Signal A must have a larger wavelength than Signal B.

  • Mechanism: Larger wavelengths diffract more efficiently, allowing Station A's waves to bend around the hills to reach the car.

Electromagnetic (EM) Spectrum

• General Properties of Electromagnetic Waves:

  • All EM waves are transverse waves.

  • All EM waves travel at the exact same speed in a vacuum/air: the speed of light, which is $300\,000\,000\,\text{ms}^{-1}$ or $3 \times 10^8\,\text{ms}^{-1}$.

  • Energy Property: The energy of an electromagnetic wave is determined by its frequency (More frequency = More energy).

• Order of the Electromagnetic Spectrum (from lowest frequency / highest wavelength to highest frequency / lowest wavelength):

  1. Radio & TV waves (highest wavelength, lowest frequency)

  2. Microwaves

  3. Infrared

  4. Visible light

  5. Ultraviolet (UV)

  6. X-rays

  7. Gamma rays (lowest wavelength, highest frequency)

Sources and Detectors of Electromagnetic Waves

• Radio Waves:

  • Source: Electronic circuits

  • Detector: Aerial

  • Speed: $3 \times 10^8\,\text{ms}^{-1}$

• Microwaves:

  • Source: Electronic circuits

  • Detector: Aerial

• Infrared:

  • Source: Electronic devices, warm objects, the Sun

  • Detector: Electronic detectors, heat-sensitive papers, black-bulb thermometer

• Visible Light:

  • Source: Electronic devices (e.g., LED), the Sun

  • Detector: Eye, photographic film, electronic components (e.g., LDR / Light Dependent Resistor)

• Ultraviolet (UV):

  • Source: The Sun, gas discharge, lamps

  • Detector: Causes fluorescence (glowing) in some objects, photographic film

• X-rays:

  • Source: Very fast electrons hitting a metal target

  • Detector: Photographic film

• Gamma Rays:

  • Source: Radioactive nuclei decaying

  • Detector: Photographic film, GM tube (Geiger-Müller tube)

Wave Behaviors: Refraction

• Definition of Refraction:

  • Refraction occurs when light changes speed (and sometimes direction) when traveling from one medium into another of different optical density.

• The Normal Line:

  • The normal line is drawn as a dotted line at $90^\circ$ (perpendicular) to the interface surface.

• Light Behavior Across Boundaries:

  • Transition from Air into Glass: The speed of light decreases. Light refracts TOWARDS the normal line.

  • Transition from Glass into Air: Light refracts AWAY from the normal line.

Units and Measurements Summary

• Sound Level Measurement:

  • Unit: Decibels (dB)