Standing Waves Law of Reflection Diffraction Interference of

-Standing Waves -Law of Reflection -Diffraction -Interference of Waves Physics Mr. Berman

Standing Wave http: //www. physics. ohio-state. edu/~ntg/reu/gifs/cont_upright_wave. gif

Standing Waves • Nodes: zero displacement • Antinodes: maximum displacement http: //sites. google. com/site/bromfieldphysics/Waves 1. JPG

Forming a Standing Wave on a Rope Incident pulse interferes with the reflected (inverted) pulse. http: //www. dacc. edu/~qchen/P 102/labs/LAB 5. HTM

How is a standing wave formed? Incident pulse Reflected pulse Standing wave http: //www. physics. utoronto. ca/~jharlow/teaching/phy 138_0708/lec 05/index_files/image 001. gif

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

Standing Waves Applet • http: //www 3. interscience. wiley. com: 8100/legacy/college/halliday/047 1320005/simulations 6 e/index. htm? newwindow=true

• L= 1/2 λ • L= 1 1/2 λ • L=2 1/2 λ • L=3 λ https: //www. sciencebuddies. org/mentoring/project_ideas/Phys_img 020. gif

Natural Frequencies of a Stretched String (Fixed Ends) Fundamental Frequency First Harmonic

Problem A string of length 1 m vibrates. The speed of the wave in the material is 400 m/s. Calculate the first three natural frequencies and draw the corresponding standing waves. Answer: 200 Hz, 400 Hz, 600 Hz

Law of Reflection • The angle of incidence equals the angle of reflection.

Refraction • When a wave crosses a boundary between two different media, the wave changes direction because it changes velocity. • Frequency is constant (as emitted from source) • Velocity change is a result of wavelength change

Refraction

Why do ocean waves approach the beach parallel to the shore? • Where is the speed greater? • Hint: check the wavelength

Diffraction • The bending of waves around a small obstacle or hole. • The smaller the wavelength the smaller the diffraction.

One Wave Two Waves Interfering