1. What are Waves? Waves are an important part of the Earth, and they’re not just in the water!

2. What exactly is a wave?  Definition: A wave is any disturbance that transmits energy through matter or space.  Waves move through matter but they do not move the matter itself Ocean waves Sound waves Light waves Radio waves Microwaves Earthquake seismic waves

3. So how are these waves different?  A wave travels through a medium (example: water, ground, air, etc.)  A vibration is one complete back and forth movement.  Mechanical waves need a medium. a medium. -These waves disturb matter. matter.  Electromagnetic waves do not need a medium. do not need a medium.

4. Types of Waves  Particles in transverse waves vibrate in an up and down motion perpendicular to the wave direction.  Particles in a longitudinal wave vibrate back and forth in the same direction that the wave travels. (Parallel to the wave direction)  At the boundary between two media transverse and longitudinal waves can combine to form surface waves.

5. Parts of a Wave Crest: the highest point (top) Trough: the lowest point (bottom)

6. Properties of Waves  Amplitude is the height of a wave. It is how much a particle in the medium is disturbed by the wave.  Wavelength is the distance between one point in a wave to the same point in the next wave.  The crest is the top of a wave  The trough is the bottom of a wave.

7. Longitudinal Waves (Also called Compressional Waves)  Compression is an area in a longitudinal wave where the particles are closer together.

8. Longitudinal Waves  Rarefaction is an area in a longitudinal wave in which the particles are spread further apart.  The amount of compression in a longitudinal (or compressional) wave is like the amplitude of a transverse wave

9. More Wave Properties  The wave speed is measured as distance divided by time (S = D/T). But it can also be calculated by multiplying wavelength by frequency. Wave speed = wavelength x frequency Wave speed = wavelength x frequency  Frequency is the number of waves that pass a given point in a certain amount of time. Frequency = speed/wavelength Frequency = speed/wavelength Frequency is measured in hertz Frequency is measured in hertz

10. More Wave Movement…  Reflection: when waves bounce off of something.  A reflected sound wave is called an echo.  Refraction: when a wave is bent at an angle and passes through a new medium.  Diffraction: when a wave is bent around a barrier or an opening.  Interference: When waves combine or overlap interference occurs.

11. More Wave Properties…  When the vibrations of one object cause another nearby to vibrate that is resonance.  Some musical instruments can use resonance to produce sound, like a marimba.

12. What are electromagnetic waves?  Electromagnetic waves do not require a medium to transfer energy (unlike mechanical waves)  These waves carry both electrical and magnetic fields. They carry the electrical field vertically and the magnetic field horizontally. They carry the electrical field vertically and the magnetic field horizontally.  The energy carried by electromagnetic waves is called electromagnetic radiation.  These waves travel at the speed of light.

13. The Electromagnetic Spectrum  The light we see is visible light.

14.  Radio waves – AM/FM Radio. Longest wavelengths Longest wavelengths  Microwaves – microwave oven  Infrared rays – used by heat lamps and night vision goggles  Visible light – the “colors” that we can see.  Ultraviolet rays – can cause skin cancer, insects use to locate nectar  X-rays – used to make images of bones.  Gamma rays – Used in cancer treatments (radiation therapy) shortest wavelengths, but carry the greatest amount of energy shortest wavelengths, but carry the greatest amount of energy

15. Wave Calculations Speed = Wavelength x Frequency Frequency = Speed/Wavelength Wavelength = Speed/Frequency Sample problem: The speed of a wave on a rope is 50 cm/second and the wavelength is 10 cm. What is the frequency?  Frequency = 50 cm/s / 10 cm  50 / 10 = 5 (5 per second) or 5 Hz

16. More sample problems  A wave has a wavelength of 5 mm and a frequency of 2 Hz. At what speed does the wave travel?  Answer: speed = wavelength x Frequency 5(mm) x 2 (Hz) = 10 mm per second 5(mm) x 2 (Hz) = 10 mm per second  The speed of a wave on a guitar string is 100 m/s and the frequency is 1000 Hz. What is the wavelength of the wave?  Answer: wavelength = speed/Frequency 100 (m/s) / 1000 (Hz) = 0.1 meter 100 (m/s) / 1000 (Hz) = 0.1 meter