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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.
d λ Physics 1051 Laboratory #6 Diffraction Part II: Introduction
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 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
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
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
You have been provided with
• Wooden stand
Strips of paper
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.
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