Paper 1 - Weak Points Flashcards
What interaction produces strange particles?
The strong interaction
What interaction do strange particles decay through?
The weak interaction
T/F: EM waves travel at different speeds in a vacuum dependent on their wavelength
False: all EM waves travel at the same speed in a vacuum
Define polarisation
The process of restricting the oscillations of particles in a transverse wave to one plane that is still perpendicular to the direction of wave propagation or energy transfer
Why can polarisation only take place in traverse waves?
Particles cannot oscillate in more than one plane in longitudinal waves because they have to oscillate parallel to the direction of wave propagation or energy transfer
What are the two directions of polarising a transverse wave?
Vertically or horizontally
Why might you see no wave transmitted after polarising it?
Because it only had components in one plane originally and they were both polarised
What is plane polarisation?
Another name for polarisation in which the oscillations of particles in a transverse wave are restricted to one plane perpendicular to the direction of wave propagation or energy transfer
What do you see if you rotate a polariser through 360 degrees?
Peaks and troughs in the intensity of the wave that looks like a sin curve
What happens to the intensity of a polarised wave?
It decreases
Which property of a wave changes when it diffracts?
The amplitude
How does the amplitude of a diffracted wave change?
The amplitude of the diffracted wave is less than that of the incident wave because the energy is distributed over a wider area
Why does diffraction occur?
When a wave passes through an aperture it is forced to curve and this causes it to interfere
What does the interference pattern formed by diffraction look like?
The interference pattern has one large and bright central maxima and then several dark fringes that have decreasing intensity on either side of it
What does the interference pattern look like if you diffract white light?
There is a central white maxima with a spectrum on either side of it
What happens to the interference pattern if you increase the wavelength of light?
You increase the angle of diffraction meaning the interference pattern gets more spread out, the fringes get wider and dimmer so fewer maxima can be seen
T/F: Increasing the wavelength has the same effect on the interference pattern as decreasing the slit width in diffraction
True
What is material dispersion?
When different wavelengths of light take different amounts of time to travel through the optical fibre because they travel at different speeds in the core
What does material dispersion cause?
Signal degradation and pulse broadening
What is model dispersion?
When different waves take different paths through the core meaning they arrive at the other end of the optical fibre at different times
What does modal dispersion cause?
Signal degradation and pulse broadening
What is the solution to material dispersion?
Use a monochromatic light source
What is the solution to modal dispersion?
Use a step index core
What is absorption in a fibre optic cable?
When the signal is absorbed by the materal
Why is absorption a problem for transmitting information via fibre optic cables?
Absorption causes a reduction in amplitude of the signal meaning it can be misinterpreted and this causes signal degradation
What is the solution to signal degradation?
Use repeaters to boost the signal
Define projectile motion
When an object experiences motion in the vertical and horizontal planes in a uniform gravitational field
Define elastic deformation
Deformation of a material that will allow it to return to its original shape after the load has been removed
Define plastic deformation
Deformation of a material that will not allow it to return to its original shape after the load has been removed
What is the name for the linear section of a force-extension graph?
The elastic region
What is the name for the curved section of a force-extension graph?
The plastic region
What is the limit of proportionality?
The point where a material stops obeying Hooke’s Law
How can we see the limit of proportionality on a force-extension graph?
The graph stops being linear
What is the elastic limit?
The point at which the material stops elastically deforming and starts plastically deforming
Define brittle material
Materials that have little to no plastic region and reach their breaking point with little to no deformation
Define ductile material
Materials that have a large plastic region meaning they reach their breaking point after a large amount of plastic deformation
What does the I-V graph look like for an ohmic conductor?
A linear graph
What does the I-V graph look like for a semiconductor diode?
y = x^3, with an point of inflection at 0
What does the I-V graph look like for a filament lamp?
A logarithmic graph in both positive and negative y
What happens to the resistance of a thermistor when the temperature increases?
The resistance increase
What happens to the resistance of an LDR when the light intensity increases?
The resistance decreases
What is superconductivity?
A property of some materials where they have zero resistivity below a critical temperature
How do you determine the critical temperature for a superconductor?
It is dependent on the material
Why do we use potential dividers?
They provide an output voltage that is a fraction of the input voltage
Define emf
The amount of chemical energy that is converted to electrical energy and transferred to a coulomb of charge when it passes through the power supply
Define lost volts
The difference between the potential difference supplied to the circuit and the emf of the cell that is due to the work done against the internal resistance of the power supply
What two conditions do you need for Young’s Double Slit experiment to be able to accurately determine the wavelength?
The screen distance must be much greater than the slit width
The path difference must be greater than half a wavelength
