![]() The maxima become narrower and the regions between darker as the number of slits is increased. Maxima can be produced at the same angles, but those for the diffraction grating are narrower and hence sharper. Idealized graphs of the intensity of light passing through a double slit (a) and a diffraction grating (b) for monochromatic light. Tiny, finger-like structures in regular patterns act as reflection gratings, producing constructive interference that gives the feathers colors not solely due to their pigmentation. Natural diffraction gratings occur in the feathers of certain birds. Figure 4 shows idealized graphs demonstrating the sharper pattern. That is, their bright regions are narrower and brighter, while their dark regions are darker. ![]() What makes them particularly useful is the fact that they form a sharper pattern than double slits do. In addition to their use as novelty items, diffraction gratings are commonly used for spectroscopic dispersion and analysis of light. Diffraction gratings work both for transmission of light, as in Figure 2, and for reflection of light, as on butterfly wings and the Australian opal in Figure 3 or the CD in Figure 1. These can be photographically mass produced rather cheaply. A diffraction grating can be manufactured by scratching glass with a sharp tool in a number of precisely positioned parallel lines, with the untouched regions acting like slits. An interference pattern is created that is very similar to the one formed by a double slit (see Figure 2). (credit: Infopro, Wikimedia Commons)Īn interesting thing happens if you pass light through a large number of evenly spaced parallel slits, called a diffraction grating. Colors such as these are direct evidence of the wave character of light. The colors reflected by this compact disc vary with angle and are not caused by pigments. (d) Use the result of part (c) to show that if the intensity at point $O$ is $I_0$, then the intensity at a point $P$ is given by Eq. 36.5a, the wave is $E = E_0$ sin $(kD - \omega t)$ and has amplitude $E_0$, as stated in part (a). ![]() (The diffuse glow surrounding the bright quasar shown in $\textbf$$ (The trigonometric identities in Appendix B will be useful.) Show that at $\theta = 0^\circ$, corresponding to point $O$ in Fig. The radiation is thought to emanate from a region just a few light-years in diameter. In this model, the radiation is emitted by interstellar gas and dust within the galaxy as this material falls toward the black hole. Of a quasar is a galaxy with a supermassive black hole at its center. P36.60 the other elongated objects in this image are normal galaxies. An example is the bright object below and to the left of center in Fig. $Quasars, an abbreviation for quasi-stellar radio sources$, are distant objects that look like stars through a telescope but that emit far more electromagnetic radiation than an entire normal Find the smallest angle away from the central maximum for which the waves would cancel after going through each of these continental gaps. As an approximation, we can model this wave's behavior by using Fraunhofer diffraction. (a) What was the wavelength of this tsunami? (b) The distance between the southern tip of Africa and northern Antarctica is about 4500 km, while the distance between the southern end of Australia and Antarctica is about 3700 km. When the wave reached the gaps between continents, it diffracted between them as through a slit. Computer models of the evolution of this enormous wave showed that it bent around the continents and spread to all the oceans of the earth. Scientists observing the wave on the open ocean measured the time between crests to be 1.0 h and the speed of the wave to be 800 km/h. This quake triggered a huge tsunami (similar to a tidal wave) that killed more than 150,000 people. On December 26, 2004, a violent earthquake of magnitude 9.1 occurred off the coast of Sumatra.
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