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?
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?
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?
Figure P22.59 shows the path of a beam of light through severallayers with different indices of refraction. (a) If Θ1 = 30.0°,what is the angle Θ2 of the emerging beam? (b) What must
the incident angle Θ1 be to have total internal reflection at thesurface between the medium with n = 1.20 and the mediumwith n = 1.00?
A lens made of glass (ng =1.52) is coated with a thin film of MgF2 (ns = 1.38) of thickness t. Visible light is incident normally on the coated lens as in Figure P24.30. (a) For what minimum value of t will the reflected light of wavelength 5.40 x 102 nm (in air) be missing? (b) Are there other values of t that will minimize the reflected light at this wavelength? Explain.
Interference effects are produced at point P on a screen as a result of direct rays from a 5.00 x 102 - nm source and reflected rays off a mirror, as shown in Figure P24.67. If the source is L = 1.00 x 102 m to the left of the screen and h = 1.00 cm above the mirror, find the distance y (in millimeters) to the first dark band above the mirror.
Chapter 38 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
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