Unit 4: Wave Nature of Light Flashcards
Particle Theory
this was the more popular theory because Newton was the main advocate, this theory believed that light consisted of a steam of fast moving particles
Classical Wave Theory
Hooke discovered the wave theory in 1655 & Huygen expanded the theory in 1678, this theory believed that light travelled as a wave, explained by Huygens principle; every point on the wave front can be considered as a point source of tiny secondary wavelets that spread out in front of the wave at the same speed as the wave itself
Rectilinear Propagation
Particle Theory- light appears to travel in a straight line since it consists of particles with high speeds
Wave Theory - the wave propagates away from the source & each point acts at a point source for a new spherical wavelet
Diffraction
Particle Theory - light can’t travel around comets like waves this is a collision between light particles at the edges of the slit
Wave Theory - when each point passes through an opening it acts as a point source for new spherical wavelets
Reflection
Particle Theory - light particles experience perfectly elastic collisions that follows the laws of motion
Wave Theory - a wave bounces off a material & travels back in the direction from which it originated
Refraction
Particle Theory - if particles speed increases it will bend toward the normal and accelerate at the boundary when passing mediums
Wave Theory - the speed of wave fronts travelling into two medias causing the waves to bend toward or away from the normal
Dispersion
Particle Theory - different colours of light have different angles of refraction & masses
Wave Theory - the white light is made of colours of the spectrum with different wavelengths for each one
Partial Reflection/Partial Refraction
Particle Theory - newtons “theory of fits” is when light sometimes arrives at a surface in a ‘fit’ of reflecton or refraction
Wave Theory - when waves move from a slow medium to a fast medium, or visa versa it experiences reflection & transmissions
Factors that affect an interference pattern
- as frequency of the sources increases, nodal lines move closer together
- when the source separation increases, the number of nodal lines increases
- if two sources are out of phase by 180, the constructive & destructive interference location changes
- if left source is delayed, the lines shift to the left
Younge’s double slit experiment
he used a single source in front of two pinholes that were very close together that was shown on a screen of interference light and dark fringes
Younge’s double slit experiemnt significance
confirm that the wave theory was true
Classical wave theory problems
what was the source vibration?
how could light travel through a vacuum such as space?
Maxwell’s Equation’s
- electric charges in space produce an electric field & currents produce a magnetic field
- magnetic field lines form continous closed loops that have neither a beginning nor end
- a changing electric field produces a magnetic field
- a changing magnetic field produces an electric field
Properties of EM waves
- EM waves are made up of alternating oscillating electric & magnetic fields
- electric & magnetic fields are perpendicular to each other & oscillate in phase
- the direction of propagation of the wave is perpendicular to both electric & magnetic
- EM waves travel at the speed of light, c, in a vacuum
State EM theory of light
oscillating charge creates an electric charge which creates an oscillating magnetic field
How did Maxwell’s equations solve classical wave theory
the changing of electric & magnetic fields create a self-propagating wave that can travel through empty space
Why do we see swirling colour when oil floats on water
different parts of the oil on water is constructive (bright-red) and destructive (dark-blue) interfernece creating the swirling oil
Difference between diffraction patterns and double slit interference patterns
- d (slit seperation) becomes w (width)
- x (distance from central max) become y
- the 1/2 was used with the minima formulas for the double slits & is now used with the maxima formulas
EM spectrum
Radiowave, microwaves, infered radiation, visable light, UV light, x-ray, gamma rays
Polarization
process of removing one of the components
How does polarizing filters work
when two polariod filters are aligned perpendicular to each other no light passes through, when they are aligned parallel light will pass through
Scattering of light
change in direction of light waves as a result of collisions
What is a diffraction grating & how does its effect interference?
- a device with a large number of equally spaced parallel slits that produces interference patterns
- interference patterns from lasers can create lines on a photographc films
