DO NOW – on loose-leaf Question: How many waves are involved in this story? Imagine that your family has just returned home from a day at the beach. You had fun playing in the ocean under a hot sun. You put some cold pizza in the microwave for dinner, and you turn on the radio. Just then, the phone rings. It’s your friend calling to ask about homework.

Answer 1. Ocean waves 2. Light waves from the sun 3. Microwaves 4. Radio waves 5. Sound waves (from the radio, telephone and voices).

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Agenda for Tuesday April 21 2015 Topic: Types of Waves Objective: SWBAT analyze info in different formats IOT distinguish between types of waves and describe their properties Agenda Do now Notes Guided Practice Graphic Organizer Exit Ticket

Types of Waves Chapter 14, Section 1

What is a Wave? A disturbance that transfers energy through matter or empty space Energy moves from one place to another Matter does not move from one place to another, just energy (ex. ocean waves)

CHECKING FOR UNDERSTANDING TRUE OR FALSE – Waves carry matter over great distances FALSE – Waves transfer energy, not matter

Medium Definition: A substance that a wave travels through (liquid, solid or gas) Waves that need a medium = MECHANICAL WAVES (ex. sound, ocean, earthquakes)

CHECKING FOR UNDERSTANDING If there is an explosion in space, could you hear it? No, because space is a vacuum and there is no medium (air) for the sound waves to travel through.

Electromagnetic Waves Waves that consist of changing electric and magnetic fields; moves at the speed of light Do not need a medium (ex – Sun produces visible light, which travels through space) Visible light, X-rays, Microwaves, TV & Radio Signals

CHECKING FOR UNDERSTANDING If there were a radio station on mars, could you possibly tune in here on Earth? Yes, if the signal were strong enough, because radio waves are electromagnetic and do not require a medium (air) to travel through.

Waves transfer energy Waves do work on objects (ex. Wave hitting the beach) The bigger the wave, the more energy it carries As the wave travels, the circles (wave front) get larger, and energy spreads out over a larger area

Vibrations & Waves Most waves are caused by vibrating objects Periodic Motion – Motion that repeats itself Simple Harmonic Motion – repeating motion in a symmetrical path around a central position (equilibrium)

Two types of Waves TRANSVERSE WAVES LONGITUDINAL WAVES

TRANSVERSE WAVES Waves vibrate in an up and down motion in perpendicular motion Particles move up and down CREST TROUGH

LONGITUDINAL WAVES Waves move back and forth in a parallel motion Particles move back and forth Compressions Rarefactions Example: SOUND WAVE

Surface Waves Occur at the boundary between two different mediums (ex – water and air) Transverse Wave + Longitudinal Wave = Surface Wave

Guided/Independent Practice Give two similarities and one difference between mechanical waves and electromagnetic waves. Answer: Both mechanical and electromagnetic waves carry energy from place to place, and both can travel through a medium. Mechanical waves require a medium to travel through, but electromagnetic waves do not.

Guided/Independent Practice 2. Why can light travel through outer space, but sound cannot? Answer: Sound waves are mechanical waves. They require a medium to travel through. There is almost no matter in outer space, so mechanical waves cannot travel through space. Light is an electromagnetic wave. Electromagnetic waves do not require a medium to travel, so they can move through outer space.

Guided/Independent Practice 3. What is the difference between how transverse waves and longitudinal waves move particles? Answer: Transverse waves cause particles to vibrate perpendicular to the direction in which the wave is traveling. Longitudinal waves cause particles to vibrate parallel to the direction in which the wave is traveling.

Guided/Independent Practice 4. A student is describing a longitudinal wave in his notebook. He writes down “The distance between crests is 3 cm.” What is wrong with what the student recorded? Answer: The student recorded data about crests, but longitudinal waves do not have crests.

Guided/Independent Practice 5. Why does a noise sound fainter as you move away from its source? Answer: The energy in the wave is spread out over a larger area, so the amount of energy in the wave at any given point is lower.

Exit Ticket Quiz What does a wave carry through matter or space? T or F: Most waves are caused by vibrating objects. Give one example of each of the following: -Mechanical Wave -Electromagnetic Wave -Transverse Wave -Longitudinal Wave

Graphic Organizer Directions: Using your notes and Ch. 14, Sec. 1 of your textbook, complete the graphic organizer below.