topic 5 Flashcards
What is a progressive wave
Waves have energy
What is Displacement
The position on a wave at a point in time, distance from equilibrium
What is amplitude
Magnitude of maximum displacement
What is frequency
The amount of full wavelengths that pass a point in a second
What is wavelength
The distance between two of the same points on a wave
What is period
The time taken for a complete wavelength to pass a point
What is phase
A point on a compete cycle in radians
What is superposition
The resultant amplitude from two waves interfering with each other
What are coherent waves
Waves with the same f and phase relationship is constant
How many nodes does a fundamental wave have
2nodes one anti-node
What is diffraction
When a waves passes through a gap with similar wavelength it will spread out into the space behind the object
How to find grating space
1*10^-3/number per mm
What is refraction
When a wave enters a medium of different density at an angle and changes direction and velocity
What is polarisation
When waves only oscillate in one plane
Can mediums polarise light?
Yes
What is path difference
The difference in wavelength between two waves
When is total internal reflection
When angle is greater than the critical angle
What is a real image
Can be projected onto a screen
On opposite side of the lens from the object
What is virtual image
Cannot be projected
Is on the same side of the lens as the object
What happens to the light in a convex lens
Light bends inwards
What happens to the light in a diverging lens
Light bends outwards
What are the properties of an electromagnetic wave
can travel through a vacuum
Can be reflected, refracted and defracted
Travels at a speed of light
What is a wave front
An imaginary plane joining points on two or more waves in phase
What is Huygens construction
each particle from a secondary wave front can be sources for secondary wavelets and form a new wave front
What is the formula for critical angle
Sin(C)=1/n
What is evidence for light as a wave
Diffraction grating = interference and polarisation
What is the evidence of light as a particle
Photoelectric effect
What is the photoelectric effect
Light exists as pockets of energy called photons
Why is planks constant used and what is quantisation
The minimal possible energy required to jump an energy level called quantisation
Evidence for electron as wave
diffraction and interference
Evidence for electron as a particle
Ionisation
What is wave particle duality
When something can act as a particle or a wave depending on the circumstances
What is the work function
The minimal energy required for electrons to leave a surface oof a material
What are photoelectrons
When electrons leave the surface of a metal
Do particles have a threshold frequency
Yes
What equation can be combined with Kinetic energy equation
1/2mv^2(max) = hf-Ф
What is the stopping voltage, and how does this relate to kinetic energy equation
The voltage required to attract all the photoelectrons back into the surface of a metal.
1/2mv^2 (max)= exV(s)
How can the work function equation be related to a graph
Ek=hf-Ф
y=mx+c
What is the ground state and what n is it
The lowest energy level an electron can be at
n=1
How do electrons get exited
If a photon with enough energy
How do electrons get exited
If a photon with enough energy collides with it
How do electrons get exited
If a photon with enough energy and correct frequency collides with it
How do electrons get exited in a gas
In gas with enough energy some wavelengths of light will be absorbed by the electrons
Do electrons de-excite on their own
Yes they will drop an energy level
How do you know when an electron has left a atom
When the diagram has an energy level of 0 mening the electron has left and ionised the atom
What is the ionisation energy
The amount of energy required for an electron to leave an atom
What is a line spectra and how is it made
Diffraction grating is used to spread out the different wavelengths of light and displaying them on a black sheet.
How can a gas line spectra be seen
Gas is heated up and looked at through a diffraction grating so the lines can be seen
Each line is shown because of electrons dropping between two energy levels
What is intensity
The amount of energy needed per unit area and per unit time
