Module 4 Part 2- Waves and Quantum Physics Flashcards
What is the difference between a transverse and a longitudinal wave
Transverse waves oscillate at 90° to the direction of energy transfer whereas longitudinal oscillations are parallel to the direction of energy transfer.
Transverse waves can travel through a vacuum but longitudinal waves need a medium to travel through
Transverse waves have peaks and troughs whereas longitudinal waves have
Compressions and rarefactions
What is amplitude
Amplitude is the distance from the peak/trough to the equilibrium position
What is wavelength
Wavelength is the distance from one peak/trough to the next
Define period of oscillation (time period)
The time a wave takes to complete one full oscillation
Define frequency
The number of wavelengths that pass a given point per second-inverse to time period
What is phase difference and what is it measured in
Phase difference is the difference between the displacements of two particles along a wave
or the displacements of two waves-this is measured in degrees° or radians where a circle is a full oscillation
What is it called when two particles reach their peak at the same time
In phase
What is it called when one particle hits its peak while the other hits its trough
Antiphase
What is reflection
Reflection is when a wave changes direction at the border between two mediums therefore remaining in the original medium-wavelength and frequency remain the same
What is the law of reflection
Angle of incidence=angle of reflection
What is refraction
Refraction is when a wave changes direction towards/away from the normal as it enters a new medium due to a change in speed which occurs when entering a more/less dense medium
What is the photoelectric effect
The photoelectric effect is when photons of electromagnetic radiation are shone onto a metal and photoelectrons are emitted off the surface
What are the conditions that need to be in place for the photoelectric effect to take place
Incident radiations frequency must be above threshold frequency of the metal-f0
What is the name given to the minimum amount of energy to free an electron
Work function-different for each metal
What is the equation that links energy, Planck constant and frequency
Energy = h x f
What happens to the spare energy after the photoelectric effect occurs
A certain amount of energy is used to overcome the work function, the rest is then transferred into to the kinetic energy of the electron
What is the idea of wave-particle duality
It is a theory that de broglie proposed which states that all matter has both wave and particle properties
What is the de broglie equation
(De broglie) Wavelength = Planck constant / momentum
What is superposition
Superposition is when two waves meet and experience either constructive or destructive interference
What is constructive interference
Constructive interference is when the amplitudes of the two waves interfering add to one another to create a larger total amplitude
What is destructive interference
Destructive interference is when two waves meet and have opposing amplitudes (one up one down) and the amplitudes subtract from one another giving a smaller total amplitude
What is path difference and what is it measured in
Path difference is the distance between a point on a diffracted wave and the source of that diffraction
it is measured in λ which is the wavelength of the wave
What is phase difference
Phase difference is the difference between two waves in the cycle of the wavelength and it is measured in degrees or radians-1 wavelength = 360° or 2pi radians
What is the equation for the young double slit experiment
Wavelength= slit separation (a) x fringe distance (x) / distance from the slits (D)
What is a standing (stationary) wave
A standing wave is when two progressive waves superimpose oppositely and form a wave which doesn’t transfer any energy and has nodes and anti-nodes
What is diffraction
Diffraction is a phenomenon unique to waves and it is when the wave is spread out after passing through a gap the same size as its wavelength-wave speed, wavelength and frequency are not altered
What is polarisation
Polarisation is unique to transverse waves and it is when a wave is confined to a single plane meaning that it only oscillates on one plane (up and down) rather than many
What is the intensity of a wave
The intensity of a wave is defined as the power passing through a surface per unit area and in any progressive wave the intensity decreases as distance from the source increases
What is the equation for intensity
I = Power / Area
What is the order of the electro magnetic waves (biggest to smallest)
Radio waves, micro waves, infra red, visible light, ultraviolet, x rays, gamma rays
What is refractive index and what is the equation for it
Refractive index is the level to which a material refracts a wave when it passes through it
Equation: refractive index (n)= speed of light in a vacuum (c) / speed of light in the material (v)
What is total internal reflection and what are the conditions for it
Total internal reflection is when all of the light on the incident boundary is reflected back into the original medium
It happens when:
-the original material has a higher refractive index
-the angle of incidence is higher than the critical angle
What are the two equations for energy of a photon
E=hf
E=hc / lambda
What fact supports the particulate nature of a photon
When the photoelectric effect occurs, the emission happens instantly rather than taking time as the wave theory suggests
What is the equation that links energy, planck constant, speed of light and wavelength
E=hc/ lambda
What is the Planck constant
6.63x10^-34
How many joules is one electron volt
1eV=1.6x10^-19 J
What is Einsteins photoelectric effect equation
E (energy) = φ (work function) + KE max
What is a piece of evidence for the wave behaviour of an electron
Electron gets diffracted when passed through a graphite film
What is fundamental frequency
Minimum frequency of a stationary wave possible on an instrument (double length of string)
It is dependent on the length, diameter, density and tension (if it’s on a string)
What does coherent mean
When two waves have both
-same frequency
-same phase difference
What is the relationship between the refractive index of a material and the angle between the wave and the normal
n is inversely proportional to sin θ
What is the relationship between path difference and phase difference
Phase difference is double path difference (for coherent waves)
What is a node
A node is a point in a stationary wave of zero displacement
What is an anti-node
An anti-node is a point in a stationary wave with maximum displacement
