why we get maxima in single-slit experiment
In a single-slit experiment, when a beam of light or a wave passes through a narrow slit and interacts with an observation screen, it can produce a pattern of alternating light and dark bands. This pattern arises due to the phenomenon of diffraction, which is the bending of waves around obstacles or the spreading of waves as they pass through narrow openings.
Here's an explanation of why you observe maxima and dark bands in a single-slit experiment:
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Wave Nature of Light: Light exhibits both particle-like and wave-like behavior. In the context of this experiment, we consider the wave-like properties of light.
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Single Slit: A beam of light or a wavefront encounters a single narrow slit in an opaque barrier. The slit acts as a diffracting aperture.
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Diffraction Pattern: When light passes through the slit, it spreads out in all directions beyond the slit's edges. This spreading is called diffraction.
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Central Maximum (Bright Band): The light waves emerging from the slit interfere with each other. At the center of the pattern, the waves are in phase, meaning their peaks and troughs align. This constructive interference results in a central maximum, a bright band at the center of the screen.
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Secondary Maxima and Minima: As you move away from the central maximum, the path lengths traveled by different parts of the wave vary. This leads to varying phase differences and interference effects.
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Secondary Maxima (Bright Bands): In some directions, the waves from the slit combine constructively, leading to secondary maxima (bright bands) on the screen. These are regions where the intensity of light is relatively high.
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Minima (Dark Bands): In other directions, the waves combine destructively, leading to minima (dark bands) on the screen. These are regions where the intensity of light is relatively low.
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Pattern Symmetry: The diffraction pattern consists of a central maximum (bright band) with alternating dark and bright bands on either side. The pattern exhibits a characteristic symmetry.
The exact positions and widths of the dark and bright bands depend on the width of the slit and the wavelength of the incident light. The narrower the slit and the longer the wavelength, the wider the central maximum and the narrower the secondary maxima and minima.