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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.
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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 a ripple in a pond is water • 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.
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 • 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.
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 • 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 • Sound also travels in 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.
References • Anatomy of the Ear - http://www.yungmd.com/images/info_ear_diagram.jpg • Sound Wave - http://www.uq.edu.au/_School_Science_Lessons/26.1.1z.GIF • Electromagnetic Spectrum - http://universe.nasa.gov/be/library/EM_Spectrum3-new.jpg • Transverse and Longitudinal Waves - http://www.itsscience.com/waves/waves.jpg
References • Direction of Particle Motion - http://www.qicomposites.com/images/fig.2.jpg • Surface Wave - http://www.pa.uky.edu/~shlosman/anim/surface_water_waves.gif