Waves and Periodic Motion PDF

Periodic Motion – Motion that repeats. Motion from a wave, pendulum or spring. Wave A wave is a disturbance that carries energy through matter or space. A wave pulse is a single bump or disturbance that travels through a medium. Two main types of waves: Mechanical Waves and Ele...

Periodic Motion – Motion that repeats. Motion from a wave, pendulum or spring. Wave A wave is a disturbance that carries energy through matter or space. A wave pulse is a single bump or disturbance that travels through a medium. Two main types of waves: Mechanical Waves and Electromagnetic Waves o Mechanical Waves require a medium. ▪ Water waves, sounds wave, waves that travel down a rope or a spring. o Electromagnetic waves such as visible light does not require a medium and travel at the speed of light. ▪ Radio, Microwaves, Infrared, Visible Light, Ultra-violet, x-rays and gamma rays. Mechanical Waves Three Types: Transverse Waves, Longitudinal Waves, and Surface Waves Transverse Wave – vibrates perpendicular to the direction of the wave’s motion. Longitudinal Wave – vibrates in the same direction as, or parallel to, the direction of the wave’s motion. Surface Wave – has both transverse and longitudinal characteristics; wave moves both perpendicular and parallel to the direction of the wave’s motion. Measuring and Describing Waves Characteristics depend on how the wave is produced or on the medium through which it travels. Characteristics that describe waves: o Speed, amplitude, wavelength, phase, period, and frequency. Speed (v) o Speed of a pulse can be determined with v = d/t o Speed of both transverse and longitudinal waves depends on the medium. Amplitude (A) – the distance from the centerline and a crest or a trough; measured in m (meters). o Amplitude and energy are proportional. o For waves that move at the same speed, the rate at which energy is transferred is proportional to the square of the amplitude. o Doubling the amplitude of a wave increases the amount of energy transferred by a factor of 4. Wavelength (λ) – the distance over which the wave’s shape repeats; the distance between identical points (adjacent crests or troughs or rest points); measured in m (meters). o Crest – the highest point on a wave. o Trough – the lowest point on a wave. Period (T) – the time it takes to complete one complete cycle; measured in s (seconds). Frequency (f) – the number of complete wavelengths in a given time; measured in Hz (hertz) Phase – any two points on a wave that are one or more whole wavelengths apart are in phase; two waves whose crests/troughs align are said to be “in-phase “. Wavelength, Frequency and Velocity Wavelength is equal to the velocity of the wave divided by the wave’s frequency 𝒗 𝝀 =𝒇 o Wavelength and frequency are inversely proportional. o As wavelength increases, frequency decreases. o As wavelength decreases, frequency increases. Wave Energy The photon energy is inversely proportional to the wavelength of the electromagnetic wave. o The energy of a photon depends on its wavelength and/or frequency. o The longer the wavelength, the less energy photons have. o The shorter the wavelength, the more energy photons have. 𝑬 = 𝒉𝒇 o E = energy in Joules o h = Planck’s Constant = 6.626 x 10-34 Js o Energy and frequency are directly proportional. ▪ As frequency increases, energy increases. ▪ As frequency decreases, energy decreases.