Recall Questions
State what is meant by the superposition principle??
When two or more waves meet at a point, the resultant displacement is the vector sum of the displacements of the individual waves.
State what is meant by coherent waves??
Waves that have a constant phase difference.
State the conditions for two waves to be coherent??
The waves must be of the same type and have the same frequency.
State what is meant by interference??
The superposition of waves from coherent sources.
State the conditions needed to observe constructive interference??
Waves must be in-phase, meaning a phase difference of $0$ or an even number of $\pi$ and a path difference of an integer number of wavelengths $(n\theta)$.
State the conditions needed to observe destructive interference??
Waves must be in anti-phase, meaning a phase difference of an odd number of $\pi$ and a path difference of $n + \frac{\lambda}{2}$.
Define the terms in the equation for $$\lambda = \frac{ax}{D}$$ and the assumption you make in deriving it??
- $\lambda$ is wavelength,
- $a$ is the slit separation,
- $x$ is the separation between adjacent fringes, and
- $D$ is the slit-screen distance.
Assumption is that $a » D$.
Why did Young setup a single slit before the double slit in his original experiment??
To ensure the waves from each of the double slits was coherent so that a stable interference pattern could be observed.
How else can inteference effects be observed, apart from using visible light??
By using a pair of speakers connected to the same power supply, or a signle microwave emitter directed at two slits in a metal plate.
Describe how a stationary wave can be formed??
The superposition of two progressive waves with the same frequency and similar amplitudes travelling in opposite directions.
State what is meant by a node on a stationary wave??
A point of zero amplitude.
State what is meant by an antinode on a stationary wave??
A point of maximum amplitude.
State the separation of adjacent nodes on a stationary wave??
$\frac{\lambda}{2}$
State the phase difference between points between adjacent nodes on a stationary wave??
$0$ radians.
State the phase difference between points on either side of a node on a stationary wave??
$180^{\circ}$ or $\pi$ radians.
State three differences between progressive waves and stationary waves (long)??
- Progressive waves transfer energy, stationary wave do not.
- The amplitude of all points on a progressive wave are the same, the amplitude of points on a stationary waves varies between $0$ and $1$.
- The phase difference between points on a progressive wave vary from $0^\circ$ to $360^\circ$, the phase difference for points in a stationary wave vary from $0^\circ$ to $180^\circ$.
State what is meant by the fundamental frequency of a stationary wave??
The lowest frequency of vibration for a given arrangement.
State what is meant by the first harmonic (fundamental mode)??
A stationary wave that has a frequency equal to the fundamental frequency. All other harmonics have a frequency that is a multiple of the fundamental frequency.
What will always be found at the ends of a stationary wave pattern produced on a vibrating string fixed at each end??
Nodes.
State how a stationary wave can be produced using sound waves (long)??
Holding a vibrating tuning fork above a pipe/tuve open at one or both ends. An increase in loudness of the sound will be heard when a stationary wave pattern is produced.
What will always be found at the ends of a stationary wave pattern formed by a column of air vibrating in a pipe/tuve closed at one end??
Node at the closed end and an antinode at the open end.
What will always be found at the ends of a stationary wave pattern formed by a column of air vibrating in an open tube/pipe?
Antinodes at both ends.
Describe how a stationary wave can be produced using microwaves (long)??
Reflect microwaves from a microwave emitter using a metal plate. The incident and reflected waves will superpose to produce a standing wave. Move a microwave detector between the emitter and metal plate to detect the presence of nodes and antinodes.
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Metadata
date: 2021-08-03 13:48
tags:
- '@?physics'
- '@?school'
- '@?public'
- '@?waves'
- '@?waves-ii'
- '@?recall-questions'
title: 'Physics - Recall for Chapter 12: Waves II'