Waves Flashcards by Ben Shep

What equation is used to calculate the Velocity of a Wave?

Velocity = Wavelength x Frequency = Wavelength / Period
V = λf = λ/t

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What is Phase Difference?

A way of describing the difference in positioning of two waves or points on waves
Inphase(0° or 360° or 2π) means that they are alligned
Antiphase(180° or π) means they are completely disalligned

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What is Path Difference?

The difference in distance or wavelength, which two waves have traveled.
Symbol is Δλ

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What are P and S Waves?

Shock waves from Earthquakes
P-Waves are Longitudinal waves, they are faster and are felt first. (P = Primary)
S-Waves are Transverse waves they are slower and feltr second. (S = Secondary)

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What is a Transverse Wave?

A wave where diplacement is perpendicular to the direction of propagation
eg. Light

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What is a Longitudinal Wave?

A wave where displacement is parrallel to the direction of propagation
eg. Sound

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What is Polarisation?

When the displacement of a wave is confined to a single direction.
It is only appliable to transverse waves
Uses include glare reducing lenses

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What is perpendicular to a surface?

Normal Line

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What connects the Angle of Incidence and Angel of Reflection?

Angle of Incidence = Angle of Reflection

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What is Refraction?

The change in direction of the travel of a wave, when changing medium

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What equation links the Speed of Light and Refractive Index?

Refractive Index = Speed of Light / Speed of Light in Medium
n=c/c(s)
c(s) is c with a lowercase s

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What is the Speed of Light in a Vacuum?

3 x 10^8

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What is Snell’s Law?

When a wave travels into a material with a higher refractive index the ray will refract toward the normal.
Into lower refractive index, refraction is away from normal

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What is the equation for Snell’s Law?

nsinθ = nsinθ
Refractive index(exiting medium) x Sin(angle of incidence) = Refraction index(entering medium) x Sin(angle of refraction)

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What is the Critical Angle?

The angle of incidence at which the angle of refraction is 90°

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What is Total Internal Reflection?

When there is no refracted ray due to the angle of incidence being to great.
All light is reflected

What conditions are needed for Total Internal Reflection?

Angle of Incidence > Critical Angle

n1 > n2

What is an Optical Fibre?

A wire for transfering data.
Central core with high refractive index
Clad with medium with a low refractive index

List Advantages of Optical fibres over Copper Wire?

Faster transmission of data (therefore more data can be sent in same time)
Cheaper to produce (can’t be stolen and melted doen like copper)
More energy effiecient (don’t get hot due to resistance)
Aren’t affected by EM induction

List problems with Optical fibres and their solutions?

Absorbtion: Not perfectly clear, thus some energy is lost.
Modal Dispertion: data is corrupted due to light taking different length paths. (Narrow fibre with one possible path)
Material Dispertion: data is corrupted due to different frequencies of light traveling at different speeds. (Monochromatic Light)

What is the Principle of Superpositition?

It states that two waves of equal wavelength can interfere to produce a wave with double th amplotude of either wave or cancel out each other

What does it mean if two sources are Coherent?

They produce wave which are:
equal in wavelength/frequency
equal in speed
constant in phase difference

What pattern is produced by Young’s Double Slit experiment?

Fringes of equal width and seperation

Central fringes have greater intensity

What did Young’s Double Slit experiment prove?

Light is a wave

Light is capable of interfering

What is the equation for Young's Double Slit experiment?

``` w = λD/s w is distance between adjacent fringes λ is wavelength D is distance between slits and screen s is distance between slits ```

What does the fringe pattern of a Single slit looks like?

A double width slit in the middle All other fringes are equally seperated Greatest intensity in the middle

What does the fringe pattern of a Diffraction Grating look like?

Serveral fringes. Central white fringe Other fringes are rainbow if white light is used All fringes have equal intensity

What is the equation for a Diffraction Grating?

``` dsinθ = nλ d is distance between slits θ is angle of a particular number of fringe λ is wavelength n is order of that particular fringe ```

Does Red or Blue deifract more?

Red difracts more due to longer wave length thant blue

What is a Stationary Wave?

A wave which is produced from the interference of two waves, with require equal speed in opposite directions and the same wavelength/frequency

What is a Node?

A point with destructive interference | where wave doesn't move and stays on the equilibrium

What is an Antinode?

A point with constructive interference | where wave is at amplitude

What is the equation for Fundemental Frequency?

``` f=(1/2L) x (T/μ)^2 f is fundemental frequency L is length of string T is tension of string μ is mass per unit length of string ```

How does Frequency differ between Progressive and Stationary Waves?

Progressive waves can have any frequency. | Stationary waves can only have certain frequencies due to the fixed nodes at the end.

How does Displacment differ between Progressive and Stationary Waves?

Progressive waves particles can move through the entire range of displacement. Stationary Waves particles oscilate to amplitude at antinodes, and don't oscilate at nodes.

How does Energy differ between Progressive and Stationary Waves?

Energy in a progressive wave is transfered in the direction of propagation. In a stationary wave energy is confined between two nodes.

How does Phase differ between Progressive and Stationary Waves?

In a progressive wave particles are not in phase within a wavelength. In a stationary wave particles are in phase when sepwerated by an odd number of nodes, and out of phase when seperated by an odd number of waves.