Waves

What is a wave?

A wave is a disturbance that carries energy through matter or space without transferring matter

Two types of mechanical waves

Transverse

Longitudinal

Transverse Waves

Particles move perpendicular to the wave’s motion

Ex: Light waves, ripples in pool

Longitudinal waves

Particles move parallel to the wave’s motion

Ex: Sound waves, Earthquake waves

Properties of transverse waves

peak/crest, trough

Properties of longitudinal waves

Compression, rarefaction

Properties of a wave

Waves and energy

Reflection

Light bounces off of a medium

The Law of Reflection

Angle of Incidence = Angle of Reflection

Clear Reflection

Smooth, Shiny surfaces have clear reflection

Diffuse Reflection

Rough, dull surfaces have a diffuse reflection. This is when light is scattered in different directions.

Refraction

Light is transmitted across a medium

Diffraction

The spreading out of waves as they pass through a gap or around an edge.

Electromagnetic Spectrum

Seven types of waves that all travel at the speed of light in a vacuum (3.0 ×10⁸ m/s).

All are transverse waves

They can travel through a vacuum (they don't need a medium like air or water).

They transfer energy from one place to another.

Electromagnetic waves

Order (Low to High Frequency): Radio, Microwave, Infrared, Visible, UV, X-ray, Gamma

Period (T)

Time taken for one full wavelength to pass a stationary point. 

Units: Seconds (s)

Frequency (f)

number of waves passing a point in a given time

Units - Hertz (Hz)

Radio Waves

Uses: Radio and television broadcasting, satellite communication.

Dangers: No known significant dangers at low intensities.

Microwaves

Uses: Cooking food (vibrating water molecules), mobile phones, and WiFi.

Dangers: Can cause internal heating of body tissues if exposure is high.

Infrared (IR)

Definition: Often called "heat radiation." Emitted by all warm objects.

Uses: Remote controls, thermal imaging, night vision, and heaters.

Dangers: Can cause skin burns and eye damage (retinal burns).

Visible Light

Definition: The only part of the spectrum the human eye can detect.

Order: Red (longest λ) to Violet (shortest λ). Uses: Human vision, photography, and fiber optic communications.

Dangers: Intense light (lasers) can cause permanent blindness.

Ultraviolet (UV)

Uses: Sunbeds, security marking (fluorescent ink), and sterilizing water/equipment.

Dangers: Sunburn, premature aging of skin, skin cancer, and cataracts.

X-rays

Definition: High-energy, ionizing waves that can pass through soft tissue but are absorbed by bone.

Uses: Medical imaging (broken bones), airport security scanners.

Dangers: Ionizing radiation; can cause cell mutation and cancer. Doctors use lead shielding for protection.

Gamma Rays

Definition: The highest frequency, shortest wavelength, and highest energy waves.

Uses: Sterilizing medical instruments, killing bacteria in food, and treating cancer (radiotherapy).

Dangers: Extremely ionizing; highly dangerous, causing severe cell damage and cancer. Requires thick lead or concrete shielding.