Concept explainers
Scientists use laser range-finding to measure the distance to the moon with great accuracy. A brief laser pulse is fired at the moon, then the time interval is measured until the “echo” is seen by a telescope. A laser beam spreads out as it travels because it diffracts through a circular exit as il leaves the laser. In order for
the reflected light to be bright enough to detect, the laser spot on the moon must be no more than 1.0 km in diameter. Staying within this diameter is accomplished by using a special large-diameter laser. If
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Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
- Find the range in wavelengths (in vacuum) for visible light in the frequency range between 4x1014 Hz (red light) and 7.9 x1014 Hz (violet light). Express the answers in nanometer. (1 nm = 10-9m)arrow_forward(a) The distance to a star is approximately 4.97 × 10¹8 m. If this star were to burn out today, in how many years would we see it disappear? years (b) How long does it take sunlight to reach Earth? minutes (c) How long does it take for a microwave radar signal to travel from Earth to the Moon and back? (The distance from Earth to the Moon is 3.84 x 105 km.) Sarrow_forwardSources A and B emit long-range radio waves of wavelength 380 m, with the phase of the emission from A ahead of that from source B by 90°. The distance rA from A to a detector is greater than the corresponding distance rB from B by 140 m. What is the magnitude of the phase difference at the detector?arrow_forward
- Sound waves diffract or bend around the edges of a doorway. Larger wavelengths diffract more than smaller wavelengths. (a) The speed of sound is 343 m/s. With what speed would a 57.0 kg person have to move through a doorway to diffract to the same extent as a 146 Hz bass tone? (b) At the speed calculated in part (a), how long in years (365.25 days) would it take the person to move a distance of one meter?arrow_forwardA laser used in LASIK eye surgery produces 55 pulses per second. The wavelength is 220.0 nm (in air), and each pulse lasts 10.0 ps. The average power emitted by the laser is 120.0 mW and the beam diameter is 0.800 mm. How long (in centimeters) is a single pulse of the laser in air?arrow_forwardThe radar system of a navy cruiser transmits at a wavelength of 1.6 cm, from a circular antenna with a diameter of 2.3 m. At a range of 6.2 km, what is the smallest distance that two speedboats can be from each other and still be resolved as two separate objects by the radar system?arrow_forward
- Given once SpaceX's StarLink can provide global internet by sending light between satellites in space, what is the expected time delay for a Whatsapp call from Indianapolis to London which is about 6416 km apart? In other words, how long does light need to travel between Indianapolis and London? µs = 1 × 10¬°s, ms = 1 × 10¬³s tdelay = 2.14µs tdelay = 2.14ms %3D tdelay = 214µs O tdelay = 2.14s %3Darrow_forwardRadiation from a distant neutron star is found by a satellite far from Earth to have wavelength λ = 3 nm. a) What is the ratio δλ/λ, where δλ is the difference with respect to the measurement by a detector on the surface of the Earth? The Schwarzschild radius of the Earth is 8.7 mm, while its actual radius is 6.4 × 106 m. b) What is the ratio δ′ λ/λ, where δ′ λ is the difference with respect to the wavelength of the same radiation at the time of emission from the neutron star’s surface? Assume that the neutron star’s actual radius is three times its (typically 4 km) Schwarzschild radius.arrow_forwardX-rays have a wavelength small enough to image individual atoms, but are challenging to detect because of their typical frequency. Suppose an X-ray camera uses X-rays with a wavelength of 3.10 nm. Calculate the frequency of the X-rays. Be sure your answer has the correct number of significant digits.arrow_forward
- Two light sources of identical strength are placed 10m apart. An object is to be placed at a point P on a line l, parallel to the line joining the light sources and at a distance d meters from it (see the figure). We want to locate P on, so that the intensity of illumination is minimized. We need to use the fact that the intensity of illumination for a single source is directly proportional to the strength of the source and inversely proportional to the square of the distance from the source. a) Find an expression for the intensity l(x) at the point P. b) If d = 5m, use graphs of l(x) and l'(x) to show that the intensity is minimized when x = 5m, that is, when P is at the midpoint of l. c) If d = 10m, show that the intensity (perhaps surprisingly) is not minimized at the midpoint. d) Somewhere between d = 5m and d = 10m there is a transitional value of d at which the point of minimal illumination abruptly changes. Estimate this value of d by graphical methods. Then find the exact value…arrow_forwardAn anstonomer on a planet orbiting the star Deneb wants to differentiate the reflected light by Earth from the light of the Sun. First, consider the area of Earths disk which reflects the Sun's intercepted light. Second, consider the surface area of a sphere with the same radius as Earths orbit around the Sun. Take the ratio of these two areas. Assume the Earths radius is 6400.0 km and is 1.3 x108 km from the Sun.arrow_forwardOften in optics scientists take advantage of effects that require very high intensity light. To get the desired effect a scientist uses a laser with power P = 0.0015 W to reach an intensity of I = 350 W/cm2 by focusing it through a lens of focal length f = 0.15 m. The beam has a radius of r = 0.0011 m when it enters the lens.Randomized VariablesP = 0.0015 WI = 350 W/cm2f = 0.15 mr = 0.0011 m Part (a) Express the radius of the beam, rp, at the point where it reaches the desired intensity in terms of the given quantities. (In other words, what radius does the beam have to have after passing through the lens in order to have the desired intensity?) Part (b) Give an expression for the tangent of the angle that the edge of the beam exits the lens with with respect to the normal to the lens surface, in terms of r and f? Part (c) Express the distance, D, between the lens's focal point and the illuminated object using tan(α) and rp. Part (d) Find the distance, D, in centimeters.arrow_forward
- College PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning