L.ocatlng the Fringes

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L.ocatlng the Fringes

Light waves produce fringes in a Young’s double-slit interference experiment, as it is called. but what exactly  determines the locations of the fringes’? To answer. we shall use the arrangement in . There. a plane wave of monochromatic light is incident on two slits SI and S2 in screen B; the light diffracts through the slits and produces an interference pattern on screen C. We draw a central axis from the point halfway between the slits to screen C as a reference. We then pick. for discussion. an arbitrary point P on the screen. at angle ()to the central axis: This point intercepts  the wave of ray rl from the bottom slit and the wave of ray r2 from the top slit.These waves are in phase when they pass through the two slits because there they are just portions of the same incident wave. However. once they have passed  the slits. the two waves must travel different distances to reach P. We saw a similar situation in Section 18-4 with sound waves and concluded that.

The phase difference between two waves can change if the waves travel paths of different
lengths.

A photograph of the interference pattern produced b~ the arrangement shown in Fig. 36-6. (The photograph is a front view of part of screen C.) The alternatingmaxima and minima are called interference fringes (because they resemble the decorative fringe sometimes used on clothing an

A photograph of the interference
pattern produced b~ the arrangement
shown in Fig. 36-6. (The photograph
is a front view of part of screen
C.) The alternatingmaxima and minima
are called interference fringes (because
they resemble the decorative
fringe sometimes used on clothing an

 

 

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L.ocatlng the Fringes