Chapter 9 Waves sound and light

A. A wave is a disturbance that moves through matter or space A. A wave is a disturbance that moves through matter or space. Waves transfer energy, not matter.

B. The particles in waves can travel in two main ways, perpendicular to motion or parallel to motion. 1. Transverse waves cause particles in matter to move at right angles to the direction in which the wave travels. a. High points are called crests. b. Low points are called troughs.

2. Compressional waves cause particles in matter to move along the same direction in which a wave travels. Places in a compressional wave where the coils are squeezed together are called compressions. Places in a compressional wave where the coils are spread apart are called rarefactions.

C. There are two main types of waves, mechanical waves and electromagnetic waves. 1. Mechanical waves can travel only through matter. Ex: sound, water 2. Electromagnetic (EM) waves can travel through both matter and space. Ex: light, radio, x-rays, microwaves, gamma rays, infrared radiation, ultraviolet radiation a. EM waves are transverse waves. b. EM waves contain electric and magnetic parts that vibrate perpendicular ┴ to the direction the wave travels.

D. The properties of waves depend on the vibrations that produce the waves. 1. The distance between one point on a wave and the nearest point moving the same speed and direction is the wavelength. a. In a transverse wave it is the distance between two adjacent crests or two adjacent troughs b. In a compressional wave it is the distance between two adjacent compressions or rarefactions c. wavelength is measured in meters (m)

2. The frequency of a wave is the number of wavelengths that pass by a point each second. Frequency is measured in units of Hertz (Hz) 3. The amplitude of a wave is the maximum distance that matter moves as the wave passes. The larger the amplitude, the more energy the wave carries.   4. The speed of a wave depends on the medium/material in which the wave travels.

E. Several wave calculations can be made. 1 E. Several wave calculations can be made. 1. wave speed = wavelength x frequency or in symbols v = λf 2. wavelength = wave speed ÷ frequency or in symbols λ = v/f 3. frequency = wave speed ÷ wavelength or in symbols f = v/ λ

F. Waves can reflect (bounce off a surface), refract (bend when it hits a new material), or diffract (bend around an obstacle).