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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- 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_forwardanswer is D, explain how?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_forwardHow far away is the Moon if a reflected beam of light takes 2.56 seconds to travel from Earth to the Moon and back. The Moon is how many kilometers from the Earth.arrow_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_forward
- Handwrittenarrow_forwardThe bright star Mintaka (also known as δ Orionis,the western most star of Orion’s belt) is extremely close to the celestial equator. Amateur astronomers can determine the field of view of their telescope (that is the angular width of the region that they can see through the telescope) by timing how long it takes Mintaka to drift through the field of view when the telescope is held stationary in hour angle. How long does it takeMintaka to drift through a 1 degree field of view?arrow_forwardIn the figure, light from ray A refracts from material 1 (n₁ = 1.73) into a thin layer of material 2 (n2 = 1.80), crosses that layer, and is then incident at the critical angle on the interface between materials 2 and 3 (n3 = 1.40). (a) What is the value of incident angle BA? (b) If 8A is decreased, does part of the light refract into material 3? Light from ray B refracts from material 1 into the thin layer, crosses that layer, and is then incident at the critical angle on the interface between materials 2 and 3. (c) What is the value of incident angle Og? (d) If Og is decreased, does part of the light refract into material 3? OB I ng no 121arrow_forward
- Often 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_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_forwardSuppose that a detector in the Hubble Space Telescope was capable of detecting visible light in the wavelength range of 400 to 700 nm. (a) List all the wavelengths for the hydrogen atom that are in this range and their series name. (b) The detector measures visible wavelengths of 537.5 nm, 480.1 nm, and 453.4 nm that researchers believe are due to the hydrogen atom. Why are all the known visible hydrogen lines not detected? (c) Use these data to calculate the speed of the stellar object that emitted the spectra. Assume that the object is not rotating. Why might rotation be an issue?arrow_forward
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