Topic 20 Flashcards
What is the principle of superposition?
When several waves pass through the same point, the curves are formed by the sum of the individual waves.
What is Light Interference
When 2 waves overlap, they can pronounce eachother or cancel each other
(Dependent on if they are in phase or not)
What is a light front?
The surface where different waves are in phase
Can be Spherical or Plane (Single Direction)
What is a ray?
A line travelling perpendicular ot the wavefront
What is Huygens-Fresnel’s Principle?
Each point on a wave front can be considered as a source of small spherical wavelets.
The observed light on a certain piint is determined by the interference of these wavelets.
Describe diffraction of light through a narrow slit.
Bending of light
Gives a pattern with stroongest intensity in the middle, fasding out in a banded pattern
What is required for visible interference?
The phase difference should be constant for a long time (Coherent Waves)
Ordinary light soruces produce incoherent light waves
Describe diffraction by a circular aperture
Gives a diffraction pattern with a bright round centre and then dark and light circles banding around it.
Give the equation indicating the first minimum for an aperture
d = Diameter of aperture
Describe the diffraction disk (Airy disk)
Image of an object - area with a focus where the image is clearer.
The resolution is dependent on the wave characteristics of light.
Equation to calculate the radius of the first dark ring of a diffraction disk
