INTRODUCTION TO WAVES

1. INTRODUCTION TO WAVES What is a Wave? www.weirdscience-discoveries.typepad.com

2. Lesson Overview • In this lesson, students will learn the concepts/terms used in wave propagation. • Discussion will then focus on the classification of waves • Briefly look at the effects of hole size in relation to wavelength in diffraction of water waves (An introduction into wave properties) www.weirdscience-discoveries.typepad.com

3. What are Mechanical Waves? Answer: Mechanical Waves are waves which propagate through a material medium. A medium is any material that allows wave propagation. Examples are solid, liquid or gas • Give two basic types of wave motions for mechanical waves. Answer:longitudinal waves and transverse waves Review of Waves Wave terminology www.weirdscience-discoveries.typepad.com

4. NOTE THE DIFFERENCE • Distinguish between longitudinal and transverse waves. • Answer: In a transverse wave, the motion of the medium is perpendicular to the motion of the wave. • In contrast to transverse waves, longitudinal are waves in which the medium moves back and forth in the same direction as the motion of the wave. www.weirdscience-discoveries.typepad.com

5. Examples of Transverse Waves • Water waves are known as transverse waves obviously because the motion of the water is up and down, or at right angles to the direction in which the waves are travelling. Other known examples are • radio waves, • light waves, and • heat waves www.weirdscience-discoveries.typepad.com

6. Examples of Longitudinal Waves • Sound waves are longitudinal waves • Why is sound wave classified as a longitudinal wave? • This is because sound waves travel back and forth in the same direction as the wave motion. www.weirdscience-discoveries.typepad.com

7. Sound Wave – A Classic Example • As a sound wave is propagated and moves out of a loud speaker to the ear of a listener, particles of air vibrate (are disturbed) back and forth in the same direction and the opposite direction of energy transport. www.weirdscience-discoveries.typepad.com

8. Mechanical and Electromagnetic Waves • What is an electromagnetic waves? An electromagnetic wave is a wave which is capable of transmitting its energy through a vacuum ( a vacuum is an empty space). www.weirdscience-discoveries.typepad.com

9. What is a Mechanical Wave? • A mechanical wave is a wave which is not capable of transmitting its energy through a vacuum (empty space) • Mechanical waves require a medium in order to transport their energy from one place (the source) to another. • Obviously sound cannot be transmitted in a vacuum hence asound wave is an example of a mechanical wave. www.weirdscience-discoveries.typepad.com

10. ABOUT DIFFRACTION OF WATER WAVES • Diffraction is one of the most interesting, and also very useful, properties of waves. • What happens when water wave strikes a barrier with a hole? • A part of the wave can move through the hole. Note: The part of the wave that strikes the wall will not move forward • Note: Diffraction can only take place if the hole in the barrier is similar in size to the wavelength of the wave. www.weirdscience-discoveries.typepad.com

11. ANIMATIONS OF WATER WAVES • Log on to the web address shown below to see Diffraction of water wave animation • http://www.ngsir.netfirms.com/englishhtm/Diffraction.htm • Log on to the web address shown below to see interference of water wave animation • http://www.ngsir.netfirms.com/englishhtm/Interference.htm www.weirdscience-discoveries.typepad.com

12. HOMEWORK/ASSESSMENT • Suggested Student Assessment: • Ask the students to research the characteristics of mechanical waves. • Distinguish between light waves and sound waves In our next lesson we shall be looking at the unique nature and properties of different wave types www.weirdscience-discoveries.typepad.com