Waves at Boundaries Reflection Interference of Waves Physics

-Waves at Boundaries -Reflection -Interference of Waves Physics Mrs. Coyle, Greece, 2009, Island of Antipaxos

How is the speed of a wave affected when a wave enters from one medium to another? • The speed depends on the medium. • It does not depend on frequency and amplitude. • It remains constant in a given medium at the same conditions. • When a wave enters a different medium, its speed changes but its frequency remains the same.

Speed of a Wave, v =lf • For a given medium, v=constant.

What does a high or low amplitude indicate? Low Amplitude High Amplitude

What happens when a wave reaches a boundary? • Part of the incident wave is transmitted and part of it is reflected.

Pulse travelling from less dense to more dense medium. • What happens to the pulse at the interface? http: //www. dacc. edu/~qchen/P 102/labs/LAB 5. HTM

Reflection of a Pulse from a Fixed End What is the direction of the reflected pulse? http: //www. dacc. edu/~qchen/P 102/labs/LAB 5. HTM

Reflection of a Wave from a Fixed End: the pulse returns inverted http: //openlearn. open. ac. uk/file. php/3524/TA 212_2_008 i. jpg

Reflection of a Pulse from a Free End What is the direction of the reflected pulse? http: //www. dacc. edu/~qchen/P 102/labs/LAB 5. HTM

Wave on a String • (Applet) http: //phet. colorado. edu/sims/wave-on-astring/wave-on-a-string_en. html

Interference • When two pulses pass the same point at the same time the waves superimpose either constructively or destructively. – Constructive Interference – Destructive Interference

Constructive Interference: resulting wave has a greater amplitude.

Destructive Interference: Resulting wave has a smaller amplitude.

• The displacements are added algebraically at the given point in time.

Interference http: //ircamera. as. arizona. edu/Nat. Sci 102/movies/interference. gif

Superposition • Simulation: Constructive and Destructive Interference (string with loose or fixed end) • http: //www 3. interscience. wiley. com: 8100/legacy/college/halliday/047 1320005/simulations 6 e/index. htm? newwindow=true

One Wave Two Waves Interfering

Interference in Water Waves