electromagnetic waves and special relitivity

electromagnetic waves and special relitivity -...

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Announcements New homework set is available on CAPA due next Wed at 10 AM Some of you have still not registered your clickers; please do so on LON-CAPA Exam next Thursday on thermodynamics, electricity and magnetism and (some) special relativity (no general relativity) as for the first exam, you can bring one sheet of notes There will be a review of the material on the exam on Tuesday Chapters 7-10

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Review: refraction and dispersion
Clicker question When light travels from a less optically dense material (smaller index of refraction) to a more optically dense material (larger index of refraction), which of the following is true? A) the wavelength increases B) the frequency increases C) the speed decreases D) the speed increases E) none of the above

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Wave optics: diffraction Like water waves passing through a breakwater, light waves spread out when passing through a narrow opening This is called diffraction We can say that the light waves spread out a great deal because they are passing through a very narrow opening compared to the size of their wavelength λ angles of dark fringes are given by formula asin θ = m λ (m=+/-1,+/-2,…), so angle from center to first dark fringe is approximately λ /a a
Wave optics: diffraction Like water waves passing through a breakwater, light waves spread out when passing through a narrow opening This is called diffraction We can say that the light waves spread out a great deal because they are passing through a very narrow opening compared to the size of their wavelength There is a broad central maximum, where the light spreads out, of width~2 λ L/a, where λ is the wavelength of the light, L is the distance to the screen and a the width of the opening

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Interference What happens if I have two waves passing through parallel small openings? The wave diffracts through both openings and the diffracted waves interfere with each other.
Inteference A series of bright and dark fringes appears on the screen. Bright for constructive interference and dark for destructive interference.

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Constructive interference When light arrives from S 1 and S 2 so that constructive interference takes place, a bright fringe results dsin θ =m λ , where m=0,+/-1,+/-2,… d θ
Destructive interference If the light arrives from S 1 and S 2 at a point on the screen and there is destructive interference, then there is a dark spot dsin θ =(m+1/2) λ , where m=0,+/-1,+/-2,…

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Diffraction grating: Let’s go crazy and put in lots of slits Light diffracts through each of the slits and we get interference between each of the diffracted waves A device like this is called a diffraction grating but there’s both diffraction and interference taking place Again, there’s a path length difference between light passing through different slits bright lines or spots when d sin θ bright = m λ m=0,1,2,…
The more slits in the grating the sharper are the interference peaks; Can also make a diffraction grating by having finely etched lines on a reflective surface

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This note was uploaded on 10/17/2011 for the course ECON 101 taught by Professor Thompson during the Spring '11 term at Michigan State University.

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electromagnetic waves and special relitivity -...

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