Waves
Objectives Determine how matter and energy interact when waves are generated. Identify and understand the three main types of mechanical waves Identify the properties of waves.
What is a wave? A wave is a disturbance that transfers energy from place to place. Energy is the ability to do work An example is the energy that is carried by a wave can lift a large ship
What causes waves? Waves form when a source of energy forces the matter (solid, liquid, or gas) to vibrate. A vibration is a repeated back and forth or up and down motion. What is the energy source in each picture?
WAVES MOVE ENERGY- NOT MATTER BOAT STAYS IN THE SAME PLACE.
Two main types of waves Mechanical waves A wave that travels only through a medium A medium is matter through which a wave travels Ocean waves travel through water (liquid) Sound waves travel through air (gas) A wave can travel along a rope (solid)
Two main types of waves Electromagnetic waves A wave that can travel through empty space or through matter. Visible light X-rays Microwaves Ultra violet light Radio waves
Electromagnetic waves are always transverse Mechanical waves can be transverse or longitudinal or a combination of both.
Mechanical Waves Three types Waves are classified by how they travel through a medium Transverse waves (A) Longitudinal waves (B) Surface waves (C) A B C
Direction of medium Types of Mechanical Waves Transverse Waves Transverse means across As a transverse wave moves in one direction, the particles of the medium move perpendicular to the direction of the wave, or across it. Direction of wave Perpendicular
Types of Mechanical Waves Longitudinal Waves The medium moves parallel to the direction the waves are traveling. The medium moves back-andforth in the same direction as the wave travels. Compression Particles are close together. Rarefaction Particles are spread out. Rarefaction Direction of wave Direction of medium Compression Parallel
Types of Mechanical Waves Surface Waves Occur at the surface between two media, such as water and air. The water moves up and down like transverse waves. The water also moves back and forth like longitudinal waves, however, water does not compress. This up and down, back and forth movement combines to make each water particle move in a circle.
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Properties of Waves The crest of a wave is the highest point *Where displacement of the medium is at a maximum
Properties of Waves The trough of a wave is the lowest point *Where the displacement of the medium is at a minimum
Properties of waves The rest position is the base line of the wave Where the medium shows no disturbance. Rest position
Properties of Waves Wavelength The distance between two corresponding parts of a wave. Crest to crest or trough to trough (transverse wave) (A) Distance from one compression to the next (longitudinal wave) (B) A B Wavelength Wavelength Wavelength Wavelength Wavelength
Properties of Waves Amplitude The vertical distance between a peak or a valley and the resting position in a transverse wave. Amplitude Amplitude
Properties of waves Frequency the number of wavelengths that pass a point each second Number of vibrations per second Measured in Hertz (hz) 1 vibration per second + 1 Hz
Property of waves The longer the wave length the lower the frequency. The shorter the wave length the higher the frequency.
Properties of waves Different waves have different amounts energy. Like earth quakes some are very damaging and some don t cause much damage at all.
Properties of Waves Properties (cont.) Speed How far the wave travels in a unit of time, or distance divided by time. The speed, wavelength, and frequency of a wave are related to each other by mathematical formulas. Unit for speed is meters per second, or m/s Speed = Wavelength x Frequency or Frequency = Speed / Wavelength or Wavelength = Speed/ Frequency
Properties of Waves Speed Problem A wave on a lake has a wavelength of 0.5 m and a frequency of 2 Hz (2 Hz = 2 per second, or 2/s). To find the speed of the wave, use this formula Speed = Wavelength x Frequency Speed = 0.5 m x 2 Hz = 0.5 m x 2/s = 1 m/s
Waves Interactions with matter sound of a knock at the door; why is it weaker to the person on the other side
Types of wave interactions Transmission Waves transmit, or carry, energy through matter Absorption some sound is absorbed by matter, like particles of the door. less sound energy will pass into the air in the next room therefore the amplitude of the wave gets smaller
Wave interactions Reflection energy that bounces back.
Wave interactions Refraction the change in direction of a wave as it changes speed, moving from one medium into another. Pencil in water looks broken due to refraction