Properties of Waves Presented by Kesler Science Essential

Properties of Waves Presented by Kesler Science

Essential Questions: 1. How do matter and energy interact when waves are generated? 2. What are three main types of mechanical waves? 3. What are properties of waves?

Properties of Waves • A disturbance that transfers energy from place to place • Remember that energy is the ability to do work • Example: The energy carried by a wave can lift a large ship.

Properties of Waves What Causes Waves • Waves are generated when a source of energy forces the matter in a medium (solid, liquid or gas) to vibrate. • Vibration – A repeated back-andforth or up-and-down motion. What is the energy source in each picture?

Properties of Waves Mechanical Waves • Mechanical waves only travel through a medium. • Examples: • Ocean waves travel through water (liquid) • Sound waves travel through air (gas) • A wave can travel along a rope (solid)

Properties of Waves Electromagnetic Waves • Some waves can travel through empty space such as: • X-rays • Visible light • Microwaves • Radio • UV - ultra violet

Quick Action – Can You Make a Wave? • Get with a partner and discuss what you know about waves. • How can you create a wave? What materials will you need? • What is the medium your wave travels through? • What was the source of energy for your wave? • Be prepared to present and discuss your wave.

Properties of Waves Three Types of Mechanical Waves • Waves are classified according to how they travel through a medium. • Transverse Waves (A) • Longitudinal Waves (B) • Surface Waves (C) A B C

Properties of Waves Transverse Waves Direction of medium • Waves that move the medium at right angles to the direction the waves are traveling. • 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 Right Angle

Properties of 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

Properties of 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.

Quick Action – Title Write About 1. Watch as your teacher demonstrates the three types of mechanical waves with a slinky. 2. Sketch and label each type of wave in your INB. 3. Describe the motion of each wave type.

Quick Action – INB Template Title INB Template 1. Cut out the template. 2. Glue it into your journal per your teacher’s instructions.

Properties of Waves Crest Wave Vocabulary • Crest – where the displacement of the medium is at a maximum • Trough – where the displacement of the medium is at a minimum • Rest position – where the medium shows no disturbance. Rest Position Trough Crest Trough

Properties of Waves Amplitude • The vertical distance between a peak or a valley and the resting position in a transverse wave. (A) • A measure of how compressed or rarefied the medium becomes in a longitudinal wave. (B) Amplitude B

Properties of Waves Properties (cont. ) 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) Wavelength A Wavelength B

Properties of Waves Properties (cont. ) Frequency • The number of complete waves (wavelengths) that pass a given point in a certain amount of time • Number of vibrations per second • Measured in units called hertz (Hz) • 1 vibration per second = 1 Hz

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

Quick Action – Frequency Problem Here is a frequency problem. Get with a partner and see if you can solve it. The speed of a wave on a rope is 50 cm/s and its wavelength is 10 cm. What is its frequency? Write the formula – Substitute and solve-

Check for Understanding Can you… • describe how matter and energy interact when waves are generated? • distinguish between the three main types of mechanical waves? • identify the properties of waves?