![]() James Gregory (1638–1675) observed the diffraction patterns caused by a bird feather, which was effectively the first diffraction grating. Isaac Newton studied these effects and attributed them to inflexion of light rays. The results of Grimaldi's observations were published posthumously in 1665. The effects of diffraction of light were first carefully observed and characterized by Francesco Maria Grimaldi, who also coined the term diffraction, from the Latin diffringere, 'to break into pieces', referring to light breaking up into different directions. Sound waves can diffract around objects, this is the reason we can still hear someone calling us even if we are hiding behind a tree.ĭiffraction can also be a concern in some technical applications it sets a fundamental limit to the resolution of a camera, telescope, or microscope. Ocean waves diffract around jetties and other obstacles. All these effects are a consequence of the fact that light is a wave.ĭiffraction can occur with any kind of wave. A shadow of a solid object, using light from a compact source, shows small fringes near its edges. Diffraction in the atmosphere by small particles can cause a bright ring to be visible around a bright light source like the sun or the moon. This principle can be extended to engineer a grating with a structure such that it will produce any diffraction pattern desired the hologram on a credit card is an example. The most colorful examples of diffraction are those involving light for example, the closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk. The effects of diffraction can be readily seen in everyday life. 5.1 Diffraction from an array of narrow slits or a grating.5 Quantitative description of diffraction.4 Qualitative observations of diffraction.1 Examples of diffraction in everyday life.The aperture or the diffracting object effectively then becomes the second source of the wave. The wave then bends around the corners of an obstacle, through apertures into the regions of the shadow of the obstacle. Note: Diffraction refers to the phenomenon of a wave encountering an opening or obstacle. Therefore to encounter diffraction on electromagnetic waves in our normal lives, we would require microwaves and not visible light since microwaves have a much higher wavelength and the longer wavelengths of about $3\ cm$ can be seen in low light conditions. This does not happen in electromagnetic waves.įor observing the phenomenon of diffraction, the order of the magnitude of the wavelength of the waves should be comparable to that of the slit width. ![]() The motion of vibration in longitudinal waves is in the same direction as the wave propagation. Sound travels by longitudinal waves which radiate outward in concentric circles. ![]() The general wavelength of visible light ranges from $7000 \times m$. The wavelength of sound generally ranges from $17\ m$ to $15\ mm$. The frequency of human audible sound waves lies from $20\ Hz$ to $20\ kHz$. The wavelength of sound waves is much higher than that of visible light. This condition is satisfied only for sound waves in everyday life. For diffraction to occur, the slit width should be comparable to the wavelength of the light or sound waves. Hint: The reason for the diffraction of sound waves being more evident in daily experience than light waves is that sound waves have much higher wavelength compared to the visible light waves. ![]()
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