Waves Flashcards
What is the photo-electric effect?
The photoelectric effect is a phenomenon in which electrons are emitted from a metal surface when it is exposed to light or other electromagnetic radiation. The photoelectric effect occurs because the energy of the light or other electromagnetic radiation is transferred to the electrons in the metal, causing them to become excited and be ejected from the surface.
What is the thresh hold frequency?
This is the minimum frequency of light required to cause the photo-electric effect.
What happens if the intensity of light is increased during the photo-electric effect?
More photo electrons Will be emitted if the frequency of the light is above the threshold frequency.
State and explain Einstein’s photoelectric equation.
hf = phi + 1/2mv^2
h = Planck’s constant
f is frequency of radiation
phi is the work function of the material in joules
1/2mv^2 is the max KE of the photoelectrons.
What is the de Broglie wavelength for a particle?
lambda = h/p
Wavelength = planck’s constant / momentum of particle.
What is wave particle duality?
This is the idea that matter and radiation can be described best by sometimes using a wave model and sometimes a particle model.
What is a progressive wave?
A wave that travels through a substance or space transferring energy.
What does out of phase mean?
Particles along a wave that move out of phase are at different points in their cycle at a particular time.
What is anti phase?
Particles along a wave that move in anti phase move in opposite directions at the same speed. The particles have opposite displacements from their mean position.
What is phase difference, how is it measured and how is it calculated?
Phase difference is measured as a fraction of the wave cycle between two points along a wave, separated by a distance x.
phi = 2pix/lambda (this gives an answer in radians)
What is an electromagnetic wave comprised of?
It has an electric field oscillation and a magnetic field oscillation acting perpendicular to each other.
What is polarisation?
This is where the oscillations of the wave are confined to one plane.
What are the effects of polarising light?
The intensity is lower as only half of the energy makes it through the filter.
What is refraction?
Refraction is the change in direction at a boundary when a wave travels from one medium to another. This happens because as a wave enters a medium with a different refractive index the wavelength increases or decreases (frequency stays the same). This only happens when the wave arrives at an angle to the medium as some parts of the wave front arrive before the other parts.
What ways do waves move when entering a medium with a higher or lower refractive index?
When entering a medium with a higher refractive index the wave refracts towards the medium and when going into a medium with a lower refractive index the wave moves away from the normal.
