Explain 3 ways the fundamental frequency of a string can be altered.

Do now: Wednesday, May 3, 2023

1) Changing the lengthShorter string = shorter λ = higher f

2) Changing the tension force in the stringTighter string = faster wave speed = higher f

3) Changing the mass per unit length of the stringHeavier string = slower wave speed = lower f

This Week’s Learning:

Reminders: 1)Standing Wave H/W is due – solutions up 2) Intereference this week – test next week

Interference of sound and E/M waves-multi-slit interference, diffraction gratings-key concept: path difference-explain rather than describe and calculate-Textbook Chapter 4 (Activity 4B, 4C)

Play with wave interference and sound (2 taps dripping, then light)

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2 Source Interference2 Source Interference Having 2 sources of Having 2 sources of

concentric waves will concentric waves will produce a pattern like produce a pattern like thisthis

There appear to be There appear to be lines radiating out lines radiating out from between the from between the sourcessources

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2 Source Interference2 Source Interference Anti-nodal lines are Anti-nodal lines are

lines of constructive lines of constructive interference. ie the interference. ie the water is choppywater is choppy

Nodal lines are lines Nodal lines are lines of destructive of destructive interference. ie the interference. ie the water is flatwater is flat

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Revision ExerciseRevision Exercise:: The n value is called The n value is called

the “order number”the “order number” It tells you how many It tells you how many

wavelengths further wavelengths further one wave has travelled one wave has travelled compared to the othercompared to the other

n = integer: antinode n = integer: antinode (constructive interference)(constructive interference)

n = half-integer: node n = half-integer: node (destructive interference)(destructive interference)

n=0

n=1

n=1

Constructive antinodal lines: Destructive nodal lines:

pd = n λpd = (n – ½) λ

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2 Source Interference2 Source Interference If the waves were If the waves were

sound, what would a sound, what would a person walking from A person walking from A to B hear? to B hear?

A series of loud and A series of loud and soft noises as they soft noises as they moved across the moved across the antinodal and nodal antinodal and nodal lineslines

A

B