Waves Flashcards
Things that are particle like behaviour
- having/ transferring kinetic energy
- having/ transferring momentum
- affected by forces such as gravity or electrostatic
Things that are wave- like behaviour
- reflection
- refraction
- polarisation
- Diffraction
- interference
De Broglie wavelength equation
Wavelength = plank constant / the particles momentum
Momentum =
Mass x Velocity
What do particles with more momentum and kinetic energy have?
They have a smaller wavelength
How can we see particles acting like a wave?
By observing them diffract while passing between gaps in atoms of graphite
What is an interference pattern?
- Where diffracted waves overlap when passing through 2 or more slits.
- where the waves arrive in phase, they add up, and this is seen as areas of brighter light and vice verca for areas where waves are out of phase/ darker because they cancel each other out.
- we call the patterns of bright spots/lines ‘fringes’
When does light give clearer interference patterns?
When the gaps it passes through are the same size as the wavelength
How can we see the de broglie equation in action?
Using an electron gun in an evacuated tube
When are standing waves formed?
- when waves are trapped, if their wavelengths ‘suit’ the space.
-this is because wavelengths interfere and constantly add up in some spaces (anti-nodes) and cancel out in other spaces (nodes)
-e.g musical instruments with a vibrating string
When can electrons orbit?
in patterns where their orbital circumference is equal to a whole number of their de-broglie wavelengths, so they can only orbit with certain velocities and certain energies.
Change in energy of an atom when it is de-excited from energy level n1 to n2 equation.
What does it mean when a transverse wave is plane-polarised?
When the vibrations stay in one plane only
Sketch a rope model and diagram to show polarisation
What is the cycle of a wave
One complete cycle of a wave is from maximum displacement to the next maximum displacement
What is the phase of a vibrating particle
– The phase of a vibrating particle at a certain time is the fraction of a cycle it has completed since the start of the cycle
– the phase difference between particles vibrating at the same frequency is the fraction of a cycle between the vibrations of the two particles, measured either in degrees or radians
– one cycle = 360° = two pi radians
Node def
Point at which the wave has no displacement
Antinode def
Maximum amplitude
What is pitch of a sound wave correlated to
Frequency
First harmonic frequency
F= c/2L
Second harmonic frequency
F=c/2L
Third harmonic frequency
F= 3C/2L
Why can only transverse waves be polarised
• in transverse waves the vibrations take place perpendicular to the direction of energy transfer • in longitudinal waves the vibrations take place in the same direction as the energy transfer
• polarisation restricts the vibrations to one plane by absorbing the vibrations at right angles to this plane
• longitudinal waves cannot be polarised because the vibrations have to take place for energy to be transmitted
What is a coherent light source
A light source which emits light waves with a constant phase difference and frequency
What are the three types of spectra in diffraction gratings
Frequency vs time period
Frequency refers to how often something happens. Period refers to the time it takes something to happen.
What is phase difference
Phase difference tells us how far apart the waves are when comparing their phases (you can think of this as their peaks and troughs).
Which electromagnetic waves have the shortest wavelengths
What do the different components of the fringe spacing equation mean?
Coherent wave source def
A source that produces waves with a constant phase difference but same wavelength
