4.4.2 Stationary Waves

Question 1

provide the properties of stationary waves

Answer 1

• superposition of two waves with the same λ & f, moving in opposite directions
• same properties as prog waves, only no energy is transferred
• wave formed has notes/antinodes (zero amp/max amp)
• two nodes are 1/2λ apart

Question 2

explain how to produce stationary waves in a string

Answer 2

• attach an oscillator to one end of a taut string w/ the other end fixed
• signal generator adjusted until stationary wave is produced
• initial wave is reflected back at note, prod. two waves w/ same frequency which superpose

Question 3

explain how to produce stationary waves with microwaves

Answer 3

• microwaves prod. w/ microwave transmitter & reflected off metal reflecting plate
• reflected & incoming waves superpose prod. stationary waves
• move microwave receiver between place & transmitter to detect nodes/antinodes
• node=min value, antinode=max value

Question 4

explain how to produce stationary waves in an air column

Answer 4

• sound source is placed at the open end of a tube, node forms at closed end
• or if there is no closed end, antinodes form at both ends

Question 5

explain how to measure the speed of sound using stationary waves

Answer 5

• place a hollow tube into a measuring cylinder of water
• choose a tuning fork & note the frequency
• tap the tuning fork & hold it above the tube, sound waves reflect off water, forming a node
• move tube up/down until you find the shortest dist. between the tube where sound resonates (sound at loudest)
• this distance = 1/2λ
• v=fλ