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WAVES Chapter 7 What is a wave A wave is –A rhythmic disturbance –Carries ENERGY but not MATTER.

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Presentation on theme: "WAVES Chapter 7 What is a wave A wave is –A rhythmic disturbance –Carries ENERGY but not MATTER."— Presentation transcript:


2 WAVES Chapter 7

3 What is a wave A wave is –A rhythmic disturbance –Carries ENERGY but not MATTER

4 How can a wave carry energy without carrying matter? Even though the ball is moving from one end of the line to the other, the people are not moving with it.

5 How do waves move Mechanical Waves Move through matter Energy moves from particle to particle Examples: –Water waves –Sound waves –Earthquake waves

6 How do waves move Electromagnetic Waves Move through empty space Do not require matter or particles in order to move Example: –Light waves

7 Types Of Waves Compressional (or Longitudinal) Waves Transverse waves

8 Parts Of A Wave distance from top of one crest to the top of the next OR from one trough to the next half the distance between the crest and trough low point of a transverse wave high point of a transverse wave

9 Properties of waves Amplitude – tells how much ENERGY the wave is carrying –B–Bright light has higher amplitude than dim –L–Loud sounds have higher amplitude than soft –L–Large water waves carry more energy than small ones

10 Wavelength (λ)– In visible light, λ determines color λ λ λ λ

11 Properties of waves Frequency – the number of λ that pass a given point in one second, measured in λ/sec = hertz –Higher frequency indicates faster vibration of whatever is generating the wave

12 Properties of waves Frequency and wavelength are closely related –Short λ creates a higher frequency In sound, this causes a higher pitch In light, violet color has a higher frequency than red –Long λ creates a lower frequency In sound, this causes a lower pitch In light, red color has a lower frequency than violet > F = < λ

13 Properties of waves Mechanical Wave Travels faster through solids because molecules are closer together and transmit the sound better Electromagnetic Wave Travels faster through empty space because there are no molecules in the way to slow it down WAVE SPEED

14 Wave Behavior Reflection: a wave strikes a surface and bounces off When sound waves reflect from a surface, it produces an ECHO. Reflection are clear when they bounce off a smooth, even surface. From a rough surface, light scatters in all directions and the reflection is distorted. HELLOOOO!!!

15 Wave Behavior Refraction: The bending of a wave as it moves from one medium into another because of a change in SPEED.

16 Wave Behavior Diffraction: The bending of waves around a barrier. SOUND WAVES You can hear sounds from a room even when you are not in the room because the sound waves bend as they pass through the open doorway LIGHT WAVES Light waves do not diffract as much as sound waves, so you can’t see around corners. This is because the λ of light is so much smaller than the width of a door. Diffraction occurs better when the barrier and λ are similar in size. WATER WAVES When water waves strike obstacles such as islands, they bend around the island and keep moving. If the island was much bigger than than the wavelength of the water wave, less diffraction would occur

17 Wave Behavior Interference: The ability of two waves to combine and form a new wave when they overlap







24 Constructive INTERFERENCE The crests of two waves – A & B – approach each other The two waves form a wave with a greater amplitude while the crests of both waves overlap

25 The original waves pass through each other and go on as they started. Constructive INTERFERENCE

26 Destructive INTERFERENCE The crest of one wave (A) approaches the trough of another (B) If the two waves have equal amplitude, they momentarily cancel when they meet

27 Destructive INTERFERENCE The original waves pass through each other and go on as they started.

28 Parts Of A Wave Parts of a COMPRESSIONAL WAVE: CompressionRarefaction Wavelength

29 What did you learn

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