Unit 1: Energy

• A wave is a vibration / disturbance that transports energy (not matter)
• A pulse is a single vibration that makes a wave, a pulse wave. Repeated pulses creates continuous or periodic waves
• The two types of waves are mechanical and electromagnetic
• mechanical waves require a medium to travel through, such as air or water.
• electromagnetic waves do not need a medium to propagate, but can travel through a medium if one is present
• The two types of mechanical waves are transverse and longitudinal waves.
• a transverse wave's motion is perpendicular to the motion of the particles in the medium.
• a longitudinal wave's motion is parallel to the motion of the particles in the medium (ex: sound wave).
• As energy travels, it causes the particles in the medium to be displaced, a wave is not matter in itself.
• The crest is the highest point in a wave.
• The trough is the lowest point in a wave.
• Equilibrium is the point where the medium rests if there was no wave.
• A wavelength is the horizontal distance in a wave cycle measured in meters.
• A wave cycle is the complete oscillation of a wave from its maximum to its minimum, returning to the same point in the same direction (up or down).
• Amplitude is the maximum displacement of a wave from equilibrium, which shows how much energy the wave is transporting, measured in meters.
• Frequency is the number of completed wave cycles in one second, measured in Hertz (Hz).
• If velocity is a constant and frequency increases, the wavelength will decrease.
• Period (T) is the amount of time needed to complete one full wave cycle, measured in seconds.
• Wave speed is its velocity, measured in meters per second.
• The velocity of a wave depends only on the nature of the medium it's travelling through.
• When the medium changes, the frequency stays the same, but the wavelength changes.
• If the medium changes and the velocity of the wave increases, the wavelength will increase.
• wavefronts are lines that represent the crests of a wave. The distance between each wavefront is a wavelength.
• Rays show a wave's direction of motion. They are drawn perpendicular to wavefronts.
• When a wave hits a boundary, reflection, refraction, or diffraction occurs.
• A boundary is the point where a wave leaves one medium and enters another.
• Reflection is when a wave encounters a boundary, part of its energy will enter the new medium, while part will "bounce back", returning to the original medium.
• When encountering a boundary, the initial wave is the incident wave.
• When encountering a boundary, the portion of the wave that enters the new medium is called the transmitted wave.
• When encountering a boundary, The part of the wave that bounces back into the original medium is called the reflected wave.
• the degree of difference in densities of media determines how much of the incident wave is reflected.
• When encountering a boundary, the more similar the densities are, the more the incident wave will be transmitted. If the media have very different densities, most of the incident wave will be reflected.
• When going from a less dense medium to a more dense medium, the reflected wave will be inverted.
• When going from a more dense medium to a less dense medium, no inversion will occur in the reflected wave.
• When a wave hits a fixed solid object, some is reflected and transmitted. The reflected end is inverted.
• If the end of a medium is left free, the reflected waves are not inverted.
• When going into a denser medium, the velocity and wavelength decrease. The opposite is true when entering a lighter medium.
• When wave speed changes as it enters a new medium, it also causes the wave to change direction, called refraction.
• Diffraction occurs when waves bend when they encounter obstacles or pass through openings.
• When a wave encounters an obstacle bigger than the wavelength, little diffraction occurs.