An idealized grating consisting of only three slits

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Unformatted text preview: ting of only three slits is represented here. P represents a point of constructive interference, ie a bright spot. P d d λ Physics 1051 Laboratory #6 Diffraction Part II: Introduction Interference To find the locations of the bright spots we first assume that the screen is far enough away from the grating so that the rays reaching a particular point P are approximately parallel when they leave the grating. The separation d between rulings is called the grating spacing. d is the distance between any two slits. The path difference, δ, between adjacent rays is δ= dsinθ, where θ is the angle from the central axis of the grating to the point P. θ d θ θ d Path length difference, δ Physics 1051 Laboratory #6 Diffraction Part II: Introduction Interference A bright spot is formed when the two rays interfere constructively, that is the path length difference between adjacent rays is an integer number of wavelengths, d sin " = m#, for m = 0, 1, 2, ... where m is the order number. This is known as the diffraction equation or the grating equation. ! Physics 1051 Laboratory #6 Part III: Apparatus and Setup Apparatus You have been provided with • • • • • • • • • Wooden stand Metre sticks Laser pointer Wooden screen Strips of paper Tape Clamps Rods Diffraction grating Diffraction Physics 1051 Laboratory #6 Diffraction Part III: Apparatus and Setup The Diffraction Grating A diffraction grating consists of a number of closely spaced slits. The s...
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