Physical science. Waves and more

Wave Basics

Types of Waves

• Mechanical Waves• Require a medium (air, water, solids).• Examples: Sound waves, water waves.

• Electromagnetic Waves• Do not need a medium; can travel through a vacuum.• Examples: Light, radio waves, X-rays.

Wave Motion

• Transverse Waves: Energy moves perpendicular to wave direction (e.g., light).

• Longitudinal Waves: Energy moves parallel to wave direction (e.g., sound).

Electromagnetic Waves

• Definition: Electric and magnetic fields transferring energy through space or matter.

• Key Features:• Travel without a medium.• Speed: 300,000,000 m/s or 3 × 10⁸ m/s in a vacuum.

Sound Waves

• Properties:• Longitudinal waves that require a medium.• Speed depends on the medium:

  • Fastest in solids (e.g., metal).

  • Slower in liquids.

  • Slowest in gases (faster in warm air than cool air).• Typical speed of sound: ~330 m/s in air (varies with temperature, pressure, and humidity).

Light Waves

• Properties:• Electromagnetic waves; do not require a medium.• Travel at a constant speed in a vacuum (3 × 10⁸ m/s).• Capable of reflection, refraction, and diffraction.

Wave Behaviors

• Reflection: Wave bounces off a surface.• Law of Reflection: Angle of incidence = Angle of reflection.

• Refraction: Wave bends when passing between mediums of different densities.• Occurs due to a change in wave speed; the amount of bending is described by Snell's Law.

• Diffraction: Wave spreads out as it passes through an opening or around an obstacle.• The degree of diffraction depends on the size of the opening relative to the wavelength; larger openings cause less diffraction.

• Interference:• Constructive Interference: Waves combine to create a larger amplitude, often leading to increased intensity.• Destructive Interference: Waves combine to reduce amplitude, potentially canceling each other out.

• Absorption: The process by which a wave’s energy is taken in by a material, often converting it to heat.• Different materials absorb different wavelengths, affecting the propagation and demonstration of waves.

• Scattering: The spreading of waves in various directions when they interact with particles or obstacles.• This effect is noticeable in phenomena such as blue skies, which result from the scattering of light by the atmosphere.

• Dispersion: The separation of light into its component colors, as in a prism, due to varying speeds of different wavelengths in a medium.

Key Formulas

• Wave Speed (v):

• Frequency (f):

• Wavelength (λ):

Example Problems

• Sound Wave Frequency• Given: Speed (v) = 330 m/s, Wavelength (λ) = 0.1 m.

• Light Wave Wavelength• Given: Speed (v) = m/s, Frequency (f) = Hz.

Key Vocabulary

• Wavelength (λ): Distance between two consecutive wave crests or troughs.

• Frequency (f): Number of wave cycles per second (measured in Hertz, Hz).

• Amplitude: Height of a wave; related to energy.

• Period (T): Time for one full wave cycle.

• Angle of Incidence: Angle at which a wave strikes a surface.

• Angle of Reflection: Angle at which a wave bounces off a surface.

Waves/Particles

• Waves: a disturbance that can carry energy

• Particles: pieces of matter

• Electromagnetic waves can behave as waves and as particles, called photons.

• Photon: massless bundles of energy

Electromagnetic Spectrum

• Electromagnetic waves give off energy in the form of electromagnetic radiation.

• There is a broad range in different types of EM radiation.

• Electromagnetic spectrum: The entire range of frequencies of electromagnetic radiation.

  • The electromagnetic spectrum is as follows in order: Radio, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, Gamma rays.

• Visible light also has a limit within the spectrum, ranging from infrared to ultraviolet.

  • Like the rainbow: Red, orange, yellow, green, blue, purple, violet, ultraviolet.

Vocab

• Wavelength (λ): The distance between two consecutive wave crests or troughs.

• Frequency (f): The number of wave cycles per second, measured in Hertz (Hz).

• Amplitude: The height of a wave, related to the energy it carries.

• Period (T): The time for one full wave cycle, calculated as T = 1/f.

• Wave Speed (v): The speed at which a wave travels, calculated as v = fλ.

• Transverse Wave: A wave where the energy moves perpendicular to the direction of wave motion.

• Longitudinal Wave: A wave where the energy moves parallel to the direction of wave motion.

• Reflection: When a wave bounces off a surface.

• Refraction: When a wave bends as it passes between two mediums with different densities.

• Diffraction: When a wave spreads out as it passes through an opening or around an obstacle.

• Constructive Interference: When waves combine to create a larger amplitude.

• Destructive Interference: When waves combine to reduce amplitude.

• Node: A point in a standing wave with no movement (zero amplitude).

• Antinode: A point in a standing wave with maximum amplitude.

• Doppler Effect: The change in frequency or wavelength of a wave due to the relative motion of the source and observer.

• Polarization: Restriction of a wave’s vibrations to a single direction.

• Resonance: Amplification of a wave when its frequency matches the natural frequency of an object.

• Pitch: The perceived highness or lowness of a sound, related to frequency.

• Echo: A reflected sound wave.

• Hertz (Hz): The unit of frequency, equal to one wave cycle per second.

• Absorption: The process by which a wave’s energy is taken in by a material, often converting it to heat.

• Scattering: The spreading of waves in various directions when they interact with particles or obstacles.

• Dispersion: The separation of light into its component colors, as in a prism.

• Intensity: The amount of energy a wave carries per unit area, related to brightness or loudness.

• Standing Wave: A wave that appears stationary, formed by the interference of two waves moving in opposite directions.

• Photon: A massless particle of light, carrying energy.

• Ultrasound: Sound waves with frequencies above 20,000 Hz (beyond human hearing).

• Infrasound: Sound waves with frequencies below 20 Hz (below human hearing).

• Medium: The material through which a wave travels (e.g., air, water, solids).

• Vacuum: Space without matter, where electromagnetic waves can travel.