waves and particle nature of light topic 5 Flashcards
what is reflection
the wave is bounced back when it hits a boundary
what is refraction
the wave changes direction as it enters a different medium, as a result of it changing speed
intensity =
power/area
polarised wave sonly oscillate in
one direction
what is the plane of polarisation
the plane in which the wave vibrates
when 2 transmission axis are at right angles to eachother..
no light passes through
at the instant the waves cross…
the displacements combine q
principle of superposition
when 2 or more waves cross, the resultant displacement equals the vector sum of the individual displacements
constructive superposition =
crest + crest or trough + trough
destructive interference =
crest + trough of equal sizes
2 points with a phase difference of 0 are
in phase
2 points with a phase difference of odd multiples of 180 degrees are
out of phase
coherent sources =
they have the same wavelength and frequency and a fixed phase difference between them
path difference =
amount by which the path travelled by one wave is longer than the other
standing wave def
the superposition of 2 progressive waves with the same wavelength, moving in opposite directions
nodes
where the amplitude of the vibration is 0
antinodes
points of maximum amplitude
equation for v on a string
route T/mass per unit length
how do electrons move down energy levels
by emitting a photon
electrons can move up energy levels if they…
absorb a photon with the exact energy difference between the 2 levels
what is the movement of an electron to a higher energy level called
excitation
what is the photoelectric effect
- free electrons on the surface of the metal absorb energy from the light
- if an electron absorbs enough energy, the bonds holding it to the metal break and the electron is released
what are the electrons released from the surface of a metal called
photoelectrons
what is the energy needed to break the bonds holding an electron the metal called
work function
threshold frequency =
work function/h
photoelectric equation, hf=
workfunction + 1/2 mv^2
increasing the intensity of light means
more photons per second on an area
