Properties of Waves and Light

Waves can be defined by their properties, important for understanding both particles and waves.
Focus on light as a wave and the concept of photons, which are particles of light that can be described as wave packets.

Momentum: Photons have momentum despite having no mass. Traditional momentum is mass × velocity, but photons defy this since they have no mass.
A beam of light consists of numerous photons acting together, forming electromagnetic waves.

Electric Field: Created by the movement of electric charges (electrons and protons).
Magnetic Field: Arises from the movement of the same charges, orthogonal to the electric field.
As the electric component increases, the magnetic component follows suit, perpendicular to it.

Amplitude: Height of the wave peaks.
Wavelength (λ): Distance between two consecutive peaks of a wave. Represented by the Greek letter lambda (λ).
Frequency (ν): Number of wave peaks that pass a point per second, measured in Hertz (Hz).
- Inverse relationship with wavelength: Longer wavelengths correlate with lower frequency.

The equation that connects speed, wavelength, and frequency:
Speed of light (c) = Wavelength (λ) × Frequency (ν)
- If either frequency or wavelength is known, the other can be calculated using this relationship.
- Speed of light: c = 3 × 10^8 m/s (constant in a vacuum).

Radio Waves: Longest wavelengths; low frequency (several meters).
Microwaves: Shorter wavelengths than radio waves (a few millimeters).
- Experiment: Observe melting patterns of chocolate chips in a microwave to see microwaves in action.
Infrared Waves: Associated with molecular motion and energy transfer.
Visible Light: The range of light humans can see; has sufficient energy to break chemical bonds.
Gamma Rays: Shortest wavelengths; highest frequency.

Constructive Interference: When waves are in phase, combining to form larger waves.
- Example: Ocean waves combining to increase wave size.
Destructive Interference: When waves are out of phase, canceling each other out.
- Example: Peaks aligning with valleys, resulting in no wave.

Occurs when waves encounter obstacles, bending around them, like water waves passing through a barrier.
Demonstrated through experiments, diffraction indicates wave-like behavior of light.

Famous experiment showing light's wave-particle duality.
Light waves pass through two slits, creating an interference pattern on a screen:
- Bright spots (constructive interference) where waves add up.
- Dark spots (destructive interference) where waves cancel each other out.

Experiment showing that light behaves as a particle:
- Low frequency light cannot eject electrons no matter how intense the light is.
- A minimum threshold frequency is required for ejection, emphasizing energy associated with frequency, not amplitude.

Light can exhibit both wave-like and particle-like properties, with interference and diffraction illustrating its wave nature and the photoelectric effect affirming its particle nature. Understanding these phenomena is crucial to grasping the behavior of light and other electromagnetic radiation.