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Homework Statement
microwave of wavelength 3 are incident to a row of parallel metal rods. The separation of the rods is 10cm. The first order diffraction is observed at 25° to the direction of the incident wave. Determine the angle between the first and the second order of diffraction maxima.
Homework Equations
I suppose that the maxima is the strip of bright fringe and this is the diffraction of single strip diffraction. I think that this picture is suitable to describe the problem,
assume that the wave 3 and 4 intersect a point P at a screen and form Bright Fringe(picture shows dark fringe, but i just assume it is bridge fringe, couldn't find a better picture).
First assumption : W4 - W3 = λ...at first maxima
and solving the triangle like how shown in this image
I get θ = mλ/a ...m is 1,2,3...and a is the size of the metal rod separation, 10cm
θ = 1 x 0.03m / 0.1m = 0.3 rad = 17.2°...but the problems say it is 25°but when I assume W4-W3 = 1.5 λ ... for first maxima
i get
θ = 1.5 x 0.03m / 0.1m = .45 rad = 25.78°...closer to the 25° stated in the question
Now my main confusion is W4-W3 for the first bright fringe λ or 1.5λ, what i am thinking now is the bright fringe is the superposition of the W4 and W3, W4 is longer than W3 by 1λ, but the question seems telling it is 1.5λ and so do some of the books and site...
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