IGCSE Physics Revision: Unit 3 Waves | for Cambridge IGCSE 2023 Syllabus

Introduction to Waves

• Revision of waves 2023 updates with added objectives concerning communication in the syllabus.

• Emphasis on understanding diverging lenses and their applications for vision correction.

• Core students introduced to microwaves and communication through satellites.

• Extended students need to understand wave types for mobile phones, Bluetooth, and optical fibers.

Types of Waves

• Definition of Waves: A wave is a transfer of energy, primarily observed through vibrations.

• Examples: Sound waves produced by vibrations in air; visible light through electromagnetic waves.

Categories of Waves

1. Mechanical Waves: Require a medium (solid, liquid, gas) to propagate.

   • Examples: Sound waves and water waves.

   • Cannot travel through a vacuum (e.g., in space).

2. Electromagnetic Waves: Do not require a medium, can travel through a vacuum.

   • Examples: Light, infrared, ultraviolet, and microwave.

Properties of Waves

• Amplitude: Maximum displacement of molecules from their mean position; indicates energy level.

• Wavelength: Distance between successive crests or troughs; represented by lambda (λ).

• Period: Time taken for one complete oscillation of a wave.

• Frequency: Number of oscillations per second measured in Hertz (Hz).

Wave Motion Types

1. Transverse Waves: Molecules vibrate perpendicular to the direction of wave motion.

   • Characterized by crests (high points) and troughs (low points).

2. Longitudinal Waves: Molecules vibrate parallel to the direction of wave motion, consisting of compressions (high-pressure regions) and rarefactions (low-pressure regions).

   • Examples: Sound waves (longitudinal) and seismic P-waves during earthquakes.

Wave Behavior

• Reflection: Change in direction when a wave hits a surface; incident angle equals reflection angle.

• Refraction: Change in speed and direction when waves pass from one medium to another (e.g., air to glass).

• Diffraction: Spreading of waves when they pass through a gap or around obstacles; dependent on wave wavelength relative to gap size.

Sound Waves

• Properties: Mechanical and longitudinal; require a medium to travel.

• Speed of Sound: 330-350 m/s in air; 1500 m/s in liquids; 5000 m/s in solids.

• Loudness and Pitch: Amplitude affects loudness (greater amplitude = louder sound); frequency affects pitch (higher frequency = higher pitch).

• Echoes: Reflection of sound waves used to determine distances by measuring time taken for the sound to return.

Light Waves & Optics

• Light Waves: Electromagnetic and transverse; speed of light approximately 3 x 10^8 m/s in a vacuum.

• Refraction in Glass: Light slows down when entering glass from air; contributing to bending towards the normal at the interface.

• Critical Angle: Angle of incidence resulting in refracted light at 90 degrees; beyond this, total internal reflection occurs.

Dispersion of Light

• White light separates into its component colors when refracted through a prism; each color bends differently based on its frequency.

• Roy G. Biv: Red to violet color spectrum, with red bending the least and violet the most.

Lenses

1. Convex Lenses (Converging): Thick in the middle, converging light rays to a focal point and forming real, inverted images on the opposite side.

   • Applications: Projectors and cameras.

2. Concave Lenses (Diverging): Thinner in the middle, spreading light rays outward, producing virtual images closer to the lens.

   • Applications: Glasses for nearsightedness.