PHYSICAL SCIENCE Waves Part 1: Types of Waves

Section 1 Types of Waves Objectives  Recognize that waves transfer energy.  Distinguish between mechanical waves and electromagnetic waves.  Explain the relationship between particle vibration and wave motion.  Distinguish between transverse waves and longitudinal waves.

What is a Wave  A wave is a disturbance that transmits energy through matter or space.  If a wave travels through matter, that matter is called the medium. The medium for an earthquake wave is earth The medium for an earthquake wave is earth The medium for a ripple in a pond is water The medium for a ripple in a pond is water The medium for sound is air The medium for sound is air  Mechanical waves are waves that require a medium through which to travel.

What is a Wave  An electromagnetic wave is a wave caused by a disturbance in electric and magnetic fields and that does not require a medium.  Electromagnetic waves are also known as light waves, of which, visible light is only a small part.  Radio waves, microwaves, X-rays, and ultraviolet waves are all types of light.

Properties of Waves Type of Wave MechanicalElectromagnetic FormLongitudinalTransverse Modeled as Transverse Medium Solids, liquids, and gases Solids and liquids None required Travel as Compressions and rarefactions in matter Back-and-forth (or up-and-down) movement in matter Oscillating electric and magnetic fields Examples Sound waves, some earthquake waves Water waves, rope waves, some earthquake waves Visible light waves, radio waves, X-rays

What is a Wave  Energy is the ability to do work.  Waves carry energy because they can do work.  A cork that bobs on the water top is evidence of work done on that cork as it is moved by the wave that passes through it.  Sound waves can do work on the eardrum and light waves can do work on the retina of the eye.

What is a Wave  The bigger a wave is, the more energy it carries.  Energy may spread out as waves travel. Sound coming from a speaker seems to be less intense as you move farther away Sound coming from a speaker seems to be less intense as you move farther away Ripples from a stone being tossed in a pond spread farther out and progressively become less intense Ripples from a stone being tossed in a pond spread farther out and progressively become less intense  As energy moves out it travels in wave fronts which increase in size causing them to spread the energy out over a larger area.

Vibrations and Waves  Most waves are caused by a vibrating object.  For example, when you speak, vocal cords in your throat move back and forth causing the air in your throat to vibrate.  The vibrations create sound waves that travel out and eventually strike our eardrums.  In the inner ear, the vibrations trigger certain frequency specific sensory cells that send impulses to the brain that are interpreted as sound.

Anatomy of the Ear

Transverse and Longitudinal Waves  Waves are often classified by the direction that the particles in the medium move as the wave passes by.  A transverse wave is a wave that causes the particles of the medium to vibrate perpendicular to the direction that the wave travels. A transverse wave may be modeled by snapping a jump rope up and watching the wave travel down the rope horizontally as the particles that make up the rope move vertically A transverse wave may be modeled by snapping a jump rope up and watching the wave travel down the rope horizontally as the particles that make up the rope move vertically Light also travels as a transverse wave Light also travels as a transverse wave

Transverse and Longitudinal Waves  A longitudinal wave is a wave that causes the particles of the medium to vibrate parallel to the direction the wave travels. A spring is useful for demonstrating a longitudinal wave as energy passes through it, the metal that makes up the spring vibrates in the same direction as the wave travels A spring is useful for demonstrating a longitudinal wave as energy passes through it, the metal that makes up the spring vibrates in the same direction as the wave travels Sound also travels in longitudinal waves Sound also travels in longitudinal waves

Transverse and Longitudinal Waves

Ocean Waves  Waves on the ocean or in a pool are surface waves.  Surface waves occur on the boundary between two different mediums.  The particles in a surface wave move both perpendicular and parallel to the direction of the wave motion.

Surface Waves

References  Anatomy of the Ear - m.jpg m.jpg m.jpg  Sound Wave - s/26.1.1z.GIF s/26.1.1z.GIF s/26.1.1z.GIF  Electromagnetic Spectrum new.jpg 3-new.jpg 3-new.jpg  Transverse and Longitudinal Waves -

References  Direction of Particle Motion - jpg jpg jpg  Surface Wave - rface_water_waves.gif rface_water_waves.gif rface_water_waves.gif