Waves

There are 2 primary types of waves: mechanical and electromagnetic Page 81 A wave is any disturbance that transmits energy through matter or empty space. Waves DO NOT transfer matter. Waves transfer energy, have certain properties, and interact in predictable ways. There are 2 primary types of waves: mechanical and electromagnetic Mechanical waves transfer energy by the vibration of particles in a medium. A medium is a substance through which a wave can travel. A medium can be a solid, a liquid, or a gas. Ex. Ocean waves, Sound waves Some waves can transfer energy without going through a medium. These waves are electromagnetic waves. Ex. Light waves, radio waves

Crest – the highest point Trough – the lowest point Page 83 Waves have similar characteristics that affect the amount of energy transferred or how it is transferred. Crest – the highest point Trough – the lowest point Wavelength – the distance between 2 consecutive crests, 2 consecutive troughs, or 2 consecutive points on a wave. It determines the frequency (number of waves that pass a given point in a unit of time. It is measured in the unit Hertz, Hz) which also affects the amount of energy. Long wavelength=low frequency=low energy Small wavelength=high frequency=high energy Amplitude – the distance between a waves rest position and crest or rest position and trough. It determines the amount of energy is transferred. Large amplitude = a lot of energy Small amplitude=a little energy

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Page 85 All waves transfer energy by repeated vibrations. However, waves can differ in many ways. Waves can be classified based on the direction in which the particles of the medium vibrate compared with the direction in which the waves move. The two main types of waves based on how they move are transverse waves and longitudinal waves. Waves in which the particles vibrate in an up-and-down (perpendicular) motion are called transverse. In a longitudinal wave, the particles of the medium vibrate back and forth (parallel) along the path that the wave moves.

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Sound waves are mechanical waves and require a medium. Page 87 A sound wave is a longitudinal wave caused by vibrations and carried through a substance. The particles of the substance, such as air particles, vibrate back and forth along the path that the sound wave travels. Sound waves are mechanical waves and require a medium. Sound waves can travel through solids (fastest), liquids and gases (slowest). The frequency of a sound wave affects its pitch (how high or low a sound seems). High frequency=high pitch (flute, Ms. Freeman) Low frequency=low pitch (tuba, Mr. Ennis) The amplitude of a sound wave affects how loud a sound is heard Larger amplitude = loud sound

Page 89 Reflection is the bouncing back of a wave after it strikes a barrier. A reflected sound wave is called an echo. An echo is heard more clearly when it bounces off a hard material versus a softer one. For sound waves, the Doppler effect is the apparent change in the frequency of a sound caused by the motion of either the listener or the source of the sound. Resonance happens when a vibrating object causes a second object to vibrate also. Ex. Loud music in a car making the windows vibrate even in the house)

Page 91 An electromagnetic wave is a wave that can travel through empty space or matter and consists of changing electric and magnetic fields. The electromagnetic spectrum is the total range of all known electromagnetic wave frequencies.

Plane mirror – flat surface; changes direction of light Page 93 Light is an electromagnetic wave. Electromagnetic waves interact in predictable ways. Reflection happens when light waves bounce off an object. The law of reflection states that the angle of incidence (angle light hits) is equal to the angle of reflection (angle light bounces off). Plane mirror – flat surface; changes direction of light Convex mirror – curved outward; light spreads apart (diverges) Concave mirror – curved inward; ; brings light together

Page 95 Refraction is the bending of a wave as it passes from one substance, or material, to another. Refraction of light waves occurs because the speed of light varies depending on the material through which the waves are traveling. White light is composed of all the wavelengths of visible light. The different wavelengths of visible light are seen by humans as different colors. When white light is refracted, the amount that the light bends depends on its wavelength.

Page 95 Diffraction is the bending or spreading of waves around barriers or through openings. The amount a wave diffracts depends on its wavelength and the size of the barrier or the opening.

Absorption is the disappearance of a wave as it strikes a medium. Page 97 Absorption is the disappearance of a wave as it strikes a medium. A transparent material allows 100% of light to be transmitted. A translucent material partially allows light to be transmitted. An opaque material does not allow any light to be transmitted. It is either absorbed (black) or reflected (white)

Page 99 When two waves meet, there can be two kinds of interference patterns; constructive and destructive. Constructive interference is when two waveforms are added together. The crests add with the crests, and the troughs add with the troughs, creating a louder sound. Destructive interference occurs when two waves are out of phase (the peaks on one line up with troughs on the other). In this, the crests cancel out the troughs, creating a diminished waveform.