{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Physics214Week13

Physics214Week13 - This Week Waves Standing waves Musical...

Info icon This preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
This Week Waves Standing waves Musical instruments, guitars, pianos, organs Interference of two waves tuning a piano, color of oil films Polarisation Why have polaroid sun glasses? Electromagnetic waves and telescopes How do we see color 10/13/2011 Physics 214 Fall 2011 1
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
10/13/2011 Physics 214 Fall 2011 2 Periodic waves One can propagate waves which are a single complicated pulse e.g. an explosion or a complicated continuous wave e.g. the wind. We will focus on regular repetitive waves These waves have a pattern which repeats and the length of one pattern is called the wavelength λ The number of patterns which pass a point/second is called the frequency f and if the time for one pattern to pass is T then f = 1/T v = λ /T = f λ λ
Image of page 2
10/13/2011 Physics 214 Fall 2011 3 Waves on a string If we shake the end of a rope we can send a wave along the rope. The rope must be under tension in order for the wave to propagate v = (F/ μ ) F = TENSION μ = MASS/UNIT LENGTH
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
10/13/2011 Physics 214 Fall 2011 4 Standing waves If two identical waves exist on the same string but traveling in opposite directions the result can be standing waves in which some points never have a deflection, these are called nodes Some points oscillate between plus and minus the maximum amplitude, these are called antinodes. Standing waves provide the notes on musical instruments. When a string is secured at both ends and plucked or hit the generated waves will travel along the string and be reflected and set up standing waves.
Image of page 4
10/13/2011 Physics 214 Fall 2011 5 Musical notes Each end of the string must be a node so the possible standing waves must be multiples of λ /2 Fundamental f = v/ λ = v/2L 2 nd Harmonic f = v/ λ = v/L 3 rd Harmonic f = v/ λ = 3v/2L Musical sound is a mixture of harmonics modified by the body of the instrument. v = (F/ μ ) so a piano or a violin is tuned by changing the tension in the string
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon