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Chapter 33: Q. 7 (page 955)
On a screen behind such a diffracting grating, narrow, bright fringes can be seen. After that, the entire research is submerged in water. Do the screen's fringes get closer together, farther apart, stay the same, or simply disappear? Explain
The fringes move away from each other.
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A radar for tracking aircraft broadcasts a microwave beam from a -diameter circular radar antenna. From a wave perspective, the antenna is a circular aperture through which the microwaves diffract.
a. What is the diameter of the radar beam at a distance of ?
b. If the antenna emits of power, what is the average microwave intensity at ?
A -diameter hole is illuminated by light of wavelength . What is the width (in mm) of the central maximum on a screen behind the slit?
Because sound is a wave, it's possible to make a diffraction grating for sound from a large board of sound-absorbing material with several parallel slits cut for sound to go through. When sound waves pass through such a grating, listeners from the grating report "loud spots" on both sides of center. What is the spacing between the slits? Use for the speed of sound.
The pinhole camera of FIGURE images distant objects by allowing only a narrow bundle of light rays to pass through the hole and strike the film. If light consisted of particles, you could make the image sharper and sharper (at the expense of getting dimmer and dimmer) by making the aperture smaller and smaller. In practice, diffraction of light by the circular aperture limits the maximum sharpness that can be obtained. Consider two distant points of light, such as two distant streetlights. Each will produce a circular diffraction pattern on the film. The two images can just barely be resolved if the central maximum of one image falls on the first dark fringe of the other image. (This is called Rayleigh’s criterion, and we will explore its implication for optical instruments in Chapter .)
a. Optimum sharpness of one image occurs when the diameter of the central maximum equals the diameter of the pinhole. What is the optimum hole size for a pinhole camera in which the film is behind the hole? Assume localid="1649089848422" an average value for visible light.
b. For this hole size, what is the angle a (in degrees) between two distant sources that can barely be resolved?
c. What is the distance between two street lights localid="1649089839579" away that can barely be resolved?
The wings of some beetles have closely spaced parallel lines of melanin, causing the wing to act as a reflection grating. Suppose sunlight shines straight onto a beetle wing. If the melanin lines on the wing are spaced apart, what is the first-order diffraction angle for green light ?
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