Section 3: Waves Flashcards
What is a progressive wave?
Carries energy from one place to another without transfering any material.
What causes a wave?
Somthing making particles or fields osscillate at a source.
What is reflection?
The wave is bounced back when it hits a boudary.
What is Refraction?
When the wave changes direction as it enters a different medium. The change in direction is a result of the wave slowing down or speeding up.
What is diffraction?
When a wave spreads out as it passes through a gap, or a round an obsicle.
What is displacment in terms of waves?
How far a point on the wave has moved from it’s undisturbed position.
What is amplitude?
The maximum magnitude of the displacement.
What is wavelength?
The length of one whole wave oscillation.
What is a period?
The time taken for one whole wave cycle.
What is the frequency?
The number of whole wave cycles per second passing a given point.
What is Phase?
A measurment of the position of a certain point along the wave cycle.
What is Phase difference?
The difference in phase between two points on a wave, radians
What is the speed of light in a vacume?
3 X 10^8 m/s
What is the speed of a sound wave?
Around 340 m/s
What is a polarised wave?
A wave that oscillates in one direction only.
What is the principle of superposition?
When two or more waves cross, the resultant displacment equals the vector sum of the individual displacements.
When does constructive interference occur?
When a trough meets another trough and peak meets peak.
When does deconstructive interference occur?
When a crest meets a trough.
Investigating resonant frequencys , what equitment is used?
signal generator
vibration transducer
string
pulley
mass
Investigating resonant frequencys, what do you do?
Find the first harmonic (a single anode and has a node at each end)
note the frequecy, keep everything the same appart from the distance between the pully and transductor
When will an emerging light ray from a semi-circular block not its change direction as it levels the block?
- Internal ray is a radius
-internal ray travels along the normal
-ray meets (glass - air) boundary at ninty degrees
-angle of incidence is zero
A circuit is set up to determine the emf and internal resistance of a cell.
it has a fixed and variable resistor in it.
explain why the studet used the fixed resistor?
- to limit (maximum) current when variable resistor is set to zero
-to prevent overheating /damage to cell - otherwise cell would discharge quickly
On a voltage/pd current graph what does the gradient give?
Resistance
Is a smaller or bigger core better for a greater pulse transmission rate?
- smaller diameter
- greater rates occur when pulses are shorter in time , there is less modal dispersion
- smaller diameter = less modal dispersion = smaller range of path lengths
Is impules a vector of scalar force?
Vector
List the order of Em waves from longest wave length to shortest. 7
Radio
Micro
Infrared
Visible
Ultraviolet
X-ray
Gamma ray
What is material dispersion?
Waves of different wavelengths travel at slightly different speeds theough an optic fibre and so reach the end of the fiber at slighlty different times, causing pulse broadening.
What is modal dispersion?
Waves enter an optical fibre at slightly different angles, meaning the distance each beam has to travel is slightly different. This leads to the beams reaching the end at different times and so cause pulse broardening.
What is Snell’s law?
A law linking a wave’s angle of incidence to its angle of refraction, with the use of the refractive indexes of the mediums involved.
How are stationary waves formed?
Stationary waves are produced by the superposition of two waves of the same frequency and amplitude travelling in opposite directions
Diffraction grattings how do you calculate number of lines per meter
N=1/d
d= distance between spaces
Diffraction gratings is one light has a longer wavelength than another how do the apperence of their maximas differ?
The longer wavelength the wider spaced the maxima are.
When does total internal refraction occur?
When the angle of incidence is greater than the critical ange
Why is there a negative sight in the a=-w^2x equation
The displacment is in the opposite direction to the acceleration vector.
State the 2 condidtions neecessary for an object to be in simple harmonic motion.
-The objects acceleration is proportional to its displacment from the equlibrium position
-This acceleration is directed towards the equilibrium position.
Antinode:
A position of maximum displacement in a stationary wave.
Coherence:
Waves are coherent if they have the same wavelength and frequency, as well as there being a fixed phase difference between them.
Electromagnetic Waves:
Waves that consist of perpendicular electric and magnetic oscillations.
Path Difference:
A measure of how far ahead a wave is compared to another wave, usually expressed in terms of the wavelength.
Pulse Broadening:
The elongation of a signal passed down an optical fibre, commonly due to modal or material dispersion.
Refractive Index:
A material property that is equal to the ratio between the speed of light in a vacuum, and the speed of light in a given material.
Stationary Wave:
A wave that stores, but does not transfer, energy.
D sin()=nx wavelength, What does d stand for?
slit spacing
Does red light have a longer or shorter wave length than blue light?
longert wave length
When is d sin(theta) = wavelength x n vaild?
If the slit-screen distance is a lot greater than the slit seperation.
