What do electromagnetic waves consist of?
- Time-varying electric and magnetic fields that oscillate perpendicular to each other and to the direction of the propagation of the wave.
The Electromagnetic SpectrumEdit
What are the types of EM waves from highest to lowest energy?
- γ rays, X-rays, UV, BVGYOR, IR, µ-rays, radio waves
Interference and DiffractionEdit
What does it mean for waves to be "coherent"?
- Their phase difference remains constant. So two coherent waves have the same wavelength.
What is the relationship between Δl and constructive vs destructive interference?
- Δl = mλ, constructive
- Δl = mλ +(1/2)λ, destructive
- m = set of all integers
Young's Double-Slit Interference ExperimentEdit
What did Young's experiment prove about the properties of light?
- Light has both particle AND wavelike properties.
What, specifically, did Young's experiment show?
- When a light wave encounters an aperture whose width is comparable to its wavelenth, the wave will fan out after it passes through. It's called diffraction.
What is the relationship of d(sinθ) and the type of interference?
- d(sinθ) = Δl = mλ = constructive
- d(sinθ) = Δl = mλ +(1/2)λ = destructive
How do you find bright fringes?
- x = L(tanθ) = distance point P is from horizontal.
- For small θ, (sinθ) is approximately (tanθ), so x = L(sinθ).
- (sinθ) = mλ/d for bright fringes, so x = Lmλ/d.
What is the relationship between m and brightness of bright fringes?
- As we move away from central maximum, we increase m, and decrease brightness. Makes sense because, for the outer fringes, light must travel farther.
What is the relationship between # of slits and sharpness of interference pattern?
- more slits is sharper. More on the constructive, and less on the destructive, the spots narrow.
What happens when there is only one slit?
- The Central maxima will be seen as very strong because of the low diffraction.
- But lower-intensity maxima will be seen because of interference from waves coming from different locations within the slit itself.
- less width of the slit --> more width of the central maximum.
What happens when light travels through a circular pinhole?
- We get circular diffusion.
Reflection and RefractionEdit
What happens when a beam of light hits a smooth, transparent surface?
- Some of its energy will be transmitted into the medium, and some will be reflected off of it.
What are angles measured against?
- the normal
What is the Law of Refraction?
- θ1 = θ1'
What is the mathematical definition of a medium's index of refraction?
- n = c/v
What is Snell's Law?
- n1(sinθ1) = n2(sinθ2)
Dispersion of LightEdit
What is dispersion?
- A variation in wave speed with frequency.
- Different frequencies have different speeds and different indices.
What is the basis of a prism?
- Different colors have different indices, so slightly different θs, resulting in the split colors.
Total Internal ReflectionEdit
What is the basis of TIR?
- As the angle of incidence increase, the angle of refraction becomes larger. When the angle of incidence reaches the critical angle, θc, the angle of refraction = 90 degrees. Any more, and there is no refraction at all, and only TIR.
What are the stipulations for TIR?
- n1 > n2
- θ1 > θc
- θc = sin-1(n1/n2)
What is a mirror?
- A mirror is an optical device which forms an image by reflecting light.
What determines where we perceive the image to be?
- The directions of the rays reflected off of the mirror.
What are the 4 questions asked about the image formed by a mirror?
- Where is the image?
- Is the image real or virtual?
- Is the image upright or inverted?
- What is the height of the image (compared to the object's)?
What is the focal length?
Where is a spherical mirror similar to a parabolic one?
What is concave vs convex?
Ray Tracing for MirrorsEdit
What is ray tracing?
What are the 3 rules governing reflection off concave mirrors?
What are the 3 rules governing reflection off convex mirrors?
How can you determine whether an image is real or virtual?
Using Equations to Answer Questions About the ImageEdit
What is the mirror equation?
What are the aspects of the sign of variables in the mirror equation?
What is the magnification equation?
How do we use it?
How does the magnification equation apply to inverted images?
How do we mathematically distinguish between concave vs convex mirrors?
What's the key difference between a lens and a mirror?
What are the two types of lenses?
Ray Tracing for LensesEdit
What are the two rules which govern converging lenses?
What are the two rules which govern diverging lenses?
Using Equations to Answer Questions about the ImageEdit
What is the focal length for converging vs diverging optical devices?