Concept explainers
The laser in a compact disc player must precisely follow the spiral track on CD, along which the distance between one loop of the spiral and the next is only about 1.25 µm. Figure P38.29 (page 1186) shows how a diffraction grating is used to provide information to keep the beam on track. The laser light passes through a diffraction grating before it reaches the CD. The strong central maximum of the diffraction pattern is used to read the information in the track of pits. The two first-order side maxima are designed to fall on the flat surfaces on both sides of the information track and are used for steering. As long as both beams are reflecting from smooth, nonpitted .surfaces, they are detected with constant high intensity. If the main beam wanders off the track, however, one of the side beams begins to strike pits on the information track and the reflected light diminishes. This change is used with an electronic circuit to guide the beam back to the desired location. Assume the laser light has a wavelength of 780 11m and the diffraction grating is positioned 6.90 µm from tike disk. Assume the first-order beams are to fall on the CD 0.400 µm on either side of the information track. What should be the number of grooves per millimeter in the grating?
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Chapter 38 Solutions
EBK PHYSICS FOR SCIENTISTS AND ENGINEER
- What is the radius of the beam of an argon laser with wavelength 454.6 nm when viewed 50.0 km away from the laser if the lasers aperture has a radius of 3.00 mm?arrow_forwardX-rays incident on a crystal with planes of atoms located 0.378 nm apart produce a diffraction pattern in which a first-order maximum is observed at an angle of 14.2. a. What is the wavelength of the X-rays incident on the crystal? b. How many orders are visible in the diffraction pattern?arrow_forwardFirst-order Bragg scattering from a certain crystal occurs at an angle of incidence of 63.8°; see figure below. The wavelength of the x-rays is 0.261nm. Assuming that the scattering is from the dashed planes shown, find the unit cell size ao. 63.8° X raysarrow_forward
- Consider a light wave passing through a slit and propagating toward a distant screen. Figure P37.53 shows the intensity variation for the pattern on the screen. Give a mathematical argument that more than 90% of the transmitted energy is in the central maximum of the diffraction pattern. Sugges- tion: You are not expected to calculate the precise percent- age, but explain the steps of your reasoning. You may use the identification 1 1 8 Imax asine -3T -27 -T 27 37 A Figure P37.53 ||arrow_forwardlet a beam of x rays of wavelength 0.125 nm be incident on an NaCl crystal at angle u 45.0° to the top face of the crystal and a family of reflecting planes. Let the reflecting planes have separation d = 0.252 nm. The crystal is turned through angle f around an axis perpendicular to the plane of the page until these reflecting planes give diffraction maxima. What are the (a) smaller and (b) larger value of f if the crystal is turned clockwise and the (c) smaller and (d) larger value of f if it is turned counterclockwise?arrow_forwardDiffraction can be used to provide a quick test of the size of red blood cells. Blood is smeared onto a slide, and a laser shines through the slide. The size of the cells is very consistent, so the multiple diffraction patterns overlap and produce an overall pattern that is similar to what a single cell would produce. Ideally, the diameter of a red blood cell should be between 7.5 and 8.0 μm. If a 633 nm laser shines through a slide and produces a pattern on a screen 24.0 cm distant, what range of sizes of the central maximum should be expected? Values outside this range might indicate a health concern and warrant further study.arrow_forward
- The pupil of an eagle's eye has a diameter of 6.0 mm. Two field mice are separated by 0.010 m. From a distance of 166 m, the eagle sees them as one unresolved object and dives toward them at a speed of 24 m/s. Assume that the eagle's eye detects light that has a wavelength of 550 nm in vacuum. How much time passes until the eagle sees the mice as separate objects? t= i eTextbook and Mediaarrow_forwardA compact disc (CD) is read from the bottom by a semiconductor laser with wavelength 790 nm passing through a plastic substrate of refractive index 1.8. When the beam encounters a pit, part of the beam is reflected from the pit and part from the flat region between the pits, so these two beams interfere with each other. What must the minimum pit depth be so that the part of the beam reflected from a pit cancels the part of the beam reflected from the flat region? (It is this cancellation that allows the player to recognize the beginning and end of a pit.)arrow_forwardInformation is stored on an audio compact disc, CD-ROM, or DVD disc in a series of pits on the disc. These pits are scanned by a laser beam. An important limitation on the amount of information that can be stored on such a disc is the width of the laser beam. Explain why this should be, and explain how using a shorter-wavelength laser allows more information to be stored on a disc of the same size. With which color of light can the Hubble Space Telescope see finer detail in a distant astronomical object: red, blue, or ultraviolet? Explain your answer.arrow_forward
- Angel is experimenting with a diffraction grating of unknown spacing. He is looking to determine the wavelength of the light in the emission spectrum of a gas and finds that a light having a known wavelength of 602.4nm is deflected by 42.1 ° away from the central maximum in the second order by this grating. Light of the wavelength to be measured is deflected by 45.7° away from the central maximum in the second order. What is the wavelength of this light in nanometers? Please give your answer as a whole number.arrow_forwardWhen an x-ray beam is scattered off the planes of a crystal, the scattered beam creates an interference pattern. This phenomenon is called Bragg scattering. For an observer to measure an interference maximum, two conditions have to be satisfied: 1. The angle of incidence has to be equal to the angle of reflection. 2. The difference in the beam's path from a source to an observer for neighboring planes has to be equal to an integer multiple of the wavelength; that is, 2d sin(0) = mx for m = 1, 2, .... The path difference 2d sin(0) can be determined from the diagram (Figure 1). The second condition is known as the Bragg condition. Figure 1 of 1 d sine d sine Review nstants Part A An x-ray beam with wavelength 0.260 nm is directed at a crystal. As the angle of incidence increases, you observe the first strong interference maximum at an angle 20.5 °. What is the spacing d between the planes of the crystal? Express your answer in nanometers to four significant figures. VE ΑΣΦ ? d = nm…arrow_forwardA large container holds two layers of liquid: a 10.0 cm thick layer of vegetable oil (ρ = 920 kg/m3 , n = 1.47) above a 20.0 cm thick layer of water (ρ = 1000 kg/m3 , n = 1.33). There is air (ρ = 1.20 kg/m3 , n = 1.0003) above the oil layer. Nia holds a red laser which emits 632.8 nm light to the right and down, so that the ray makes an angle of 50.0° relative to a line normal to the oil layer a) What is the angle of incidence at the oil→ water interface? ________________________ b) What is the angle of reflection at the oil→ water interface? ________________________ c) What is the angle of refraction at the oil→ water interface? ________________________ d) What is the frequency of the light in the air? ________________________ e) What is the wavelength of the light in the oil? ________________________ f) What is the speed of the light in the water? ________________________ g) Nia looks into the tank and sees where the laser light impinges on the bottom of the container. She names this…arrow_forward
- Modern PhysicsPhysicsISBN:9781111794378Author:Raymond A. Serway, Clement J. Moses, Curt A. MoyerPublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning