Nature and Properties of Light Flashcards
Learn the basics
Define speed with regards to light.
v, The wave speed of light is constant and depends on in what medium it travels. In vacuum it’s c.
c = 2.99 × 108 m/s.
Define frequency with regards to light.
Number of waves that pass a given point in one second. Cycles per second, Hz.
f = 1/τ = v/λ.
Define wavelength with regards to light.
The distance until the wave comes back to the same amplitude. λ
Define energy with regards to light.
Light moves energy from one place to another, w/o moving mass. Energy depends on frequency.
Give examples of when light exhibit wave nature and when it exhibit particle nature.
Wave nature:
Principles: Reflection & refraction
Examples: Mirrors, prisms, lenses, fiber.
Particle nature:
Principles: Interference, diffraction, polarization.
Examples: Thin coatings on mirror, quarter-wave plates, gratings.
Describe the six properties of electromagnetic waves.
Polarization, Superposition, reflection, refraction, diffraction & interference.
What causes light to be polarized?
It arises from the direction of the E-field vector with respect to the direction of the light’s propagation. Certain materials will transmit only selected polarizations.
I(θ) = I_0 cos^2 (θ)
Describe Huygens’ principle.
Each point along a wave front can be considered a point source for production of secondary spherical wavelets. The position of the wave front, after a time period, will be the surface tangent to these secondary wavelets.
Describe the superposition principle.
Two or more waves can traverse the same space at the same time independently of one another. The electric field at any point in space is simply the vector sum of the electric fields of the individual waves at that point.
Define the terms reflection, refraction, and index of refraction.
Reflection: Light that reflects off a surface. The law of reflection states that the angle of incidence on a reflecting basic surface is equal to the angle of reflection.
Refraction: A change in direction when a ray of light passes from one medium to another. Caused by the difference in speed of the wave in the media.
Index of refraction (n): The ratio of the speed difference of the refracting materials.
Describe Snell’s law.
The ratio of the indices of refraction and the direction of the two rays of light for the two media.
n_1/n_2 = sinθ/sinφ. (θ infallsvinkel, φ refraktionsvinkel.
Explain diffraction and interference in terms of Huygens’ principle.
Since Huygens principle states that a point in the wavefront can be regarded as a point source light naturally “bends” around corners -> thus creating diffraction.
Having two or more point sources some distance apart will produce waves that interfere with each other (superposition principle).
