College Physics: A Strategic Approach (3rd Edition)
3rd Edition
ISBN: 9780321879721
Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
Publisher: PEARSON
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Chapter 29, Problem 75GP
To determine
Minimum intensity of the laser beam during each pulse.
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A ruby laser emits an intense pulse of light that lasts a mere 10 ns . The light has a wavelength of 690 nm , and each pulse has an energy of 400 mJ .
How many photons are emitted in each pulse?
What is the rate of photon emission, in photons per second, during the 10 nsns that the laser is "on"?
Fluorescence microscopy, discussed in Section 29.8, is an important tool in modern cell biology. A variation on this technique depends on a phenomenon known as two-photon excitation.If two photons are absorbed simultaneously (i.e., withinabout 10-16 s), their energies can add. A molecule that is normallyexcited by a 350 nm photon can be excited by two photonseach having half as much energy. For this process to beuseful, photons must illuminate the sample at the very high rateof at least 1029 photons/m2 # s. This is achieved by focusing alaser beam to a small spot and by concentrating the power ofthe laser into very short 110-13 s2 pulses that are fired 108 timeseach second. Suppose a biologist wants to use two-photon excitationto excite a molecular species that would be excited by500 nm light in normal one-photon fluorescence microscopy.What minimum intensity 1W/m2 2 must the laser beam haveduring each pulse?
Fluorescence microscopy, discussed is an important tool in modern cell biology. A variation on this technique depends on a phenomenon known as two-photon excitation. If two photons are absorbed simultaneously (i.e., within about 10-16 s), their energies can add. A molecule that is normallyexcited by a 350 nm photon can be excited by two photons each having half as much energy. For this process to be useful, photons must illuminate the sample at the very high rate of at least 1029 photons/m2 ⋅ s. This is achieved by focusing a laser beam to a small spot and by concentrating the power of the laser into very short (10-13 s) pulses that are fired 108 timeseach second. Suppose a biologist wants to use two-photon excitationto excite a molecular species that would be excited by 500 nm light in normal one-photon fluorescence microscopy. What minimum intensity (W/m2) must the laser beam have during each pulse?
Chapter 29 Solutions
College Physics: A Strategic Approach (3rd Edition)
Ch. 29 - Prob. 1CQCh. 29 - Prob. 2CQCh. 29 - Prob. 3CQCh. 29 - Prob. 4CQCh. 29 - Prob. 5CQCh. 29 - Prob. 6CQCh. 29 - Prob. 7CQCh. 29 - Prob. 8CQCh. 29 - Prob. 9CQCh. 29 - Prob. 10CQ
Ch. 29 - Prob. 11CQCh. 29 - Prob. 12CQCh. 29 - Prob. 13CQCh. 29 - Prob. 14CQCh. 29 - Prob. 15CQCh. 29 - Prob. 16CQCh. 29 - Prob. 17CQCh. 29 - Prob. 18CQCh. 29 - Prob. 19CQCh. 29 - Prob. 20CQCh. 29 - Prob. 21CQCh. 29 - Prob. 22CQCh. 29 - Prob. 23CQCh. 29 - Prob. 24MCQCh. 29 - Prob. 25MCQCh. 29 - Prob. 26MCQCh. 29 - Prob. 27MCQCh. 29 - Prob. 28MCQCh. 29 - Prob. 29MCQCh. 29 - Prob. 30MCQCh. 29 - Prob. 1PCh. 29 - Prob. 2PCh. 29 - Prob. 3PCh. 29 - Prob. 4PCh. 29 - Prob. 5PCh. 29 - Prob. 6PCh. 29 - Prob. 7PCh. 29 - Prob. 8PCh. 29 - Prob. 9PCh. 29 - Prob. 10PCh. 29 - Prob. 11PCh. 29 - Prob. 12PCh. 29 - Prob. 13PCh. 29 - Prob. 14PCh. 29 - Prob. 15PCh. 29 - Prob. 16PCh. 29 - Prob. 17PCh. 29 - Prob. 18PCh. 29 - Prob. 19PCh. 29 - Prob. 21PCh. 29 - Prob. 22PCh. 29 - Prob. 23PCh. 29 - Prob. 24PCh. 29 - Prob. 25PCh. 29 - Prob. 26PCh. 29 - Prob. 27PCh. 29 - Prob. 28PCh. 29 - Prob. 29PCh. 29 - Prob. 30PCh. 29 - Prob. 31PCh. 29 - Prob. 32PCh. 29 - Prob. 33PCh. 29 - Prob. 34PCh. 29 - Prob. 35PCh. 29 - Prob. 36PCh. 29 - Prob. 37PCh. 29 - Prob. 38PCh. 29 - Prob. 39PCh. 29 - Prob. 40PCh. 29 - Prob. 41PCh. 29 - Prob. 42PCh. 29 - Prob. 43PCh. 29 - Prob. 44GPCh. 29 - Prob. 45GPCh. 29 - Prob. 46GPCh. 29 - Prob. 47GPCh. 29 - Prob. 48GPCh. 29 - Prob. 49GPCh. 29 - Prob. 50GPCh. 29 - Prob. 51GPCh. 29 - Prob. 52GPCh. 29 - Prob. 53GPCh. 29 - Prob. 54GPCh. 29 - Prob. 55GPCh. 29 - Prob. 56GPCh. 29 - Prob. 57GPCh. 29 - Prob. 58GPCh. 29 - Prob. 59GPCh. 29 - Prob. 60GPCh. 29 - Prob. 61GPCh. 29 - Prob. 62GPCh. 29 - Prob. 63GPCh. 29 - Prob. 64GPCh. 29 - Prob. 65GPCh. 29 - Prob. 66GPCh. 29 - Prob. 67GPCh. 29 - Prob. 68GPCh. 29 - Prob. 69GPCh. 29 - Prob. 70GPCh. 29 - Prob. 71GPCh. 29 - Prob. 73GPCh. 29 - Prob. 74GPCh. 29 - Prob. 75GPCh. 29 - Prob. 76MSPPCh. 29 - Prob. 77MSPPCh. 29 - Prob. 78MSPPCh. 29 - Prob. 79MSPP
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- Exposure to a sufficient quantity of ultraviolet light will redden the skin, producing erythema—a sunburn. The amount of exposure necessary to produce this reddening depends on the wavelength. For a 1.0 cm2 patch of skin, 3.7 mJ of ultraviolet light at a wavelength of 254 nm will produce reddening; at 300 nm wavelength, 13 mJ are required.a. What is the photon energy corresponding to each of these wavelengths?b. How many total photons does each of these exposures correspond to?c. Explain why there is a difference in the number of photons needed to provoke a response in the two cases.arrow_forwardA 633 nm helium-neon laser puts out 4.00 W of power with a beam 5.70 mm in diameter. The beam is pointed directly at a pinhole which has a diameter of 1.80 mm. How many photons of light will travel through the pinhole per second? Assume that the intensity of the light is equally distributed across the whole area of the beam. number of photons per second: photons/sarrow_forwardA 1.00 mW helium-neon laser emits a visible laser beam with a wavelength of 633 nm. How many photons are emitted per second?arrow_forward
- One molecule of ATP provides 0.30 eV when it is used to power cellular processes. Photosynthesis in a typical plant requires 8 photons at 550 nm to produce 1 molecule of ATP. What is the overall efficiency of this process?arrow_forwardA certain helium-neon laser pointer, emitting light with a wavelength of 632 nm, has a beam with an intensity of 715 W/m2 and a diameter of 2.70 mm. How many photons are emitted by the laser pointer every second? Thank you for the help!arrow_forwardA beam of 400 nm light is adjusted to have the same intensity as a beam of 600 nm light. How does the number of photons in the 400nm beam, N400 compare to the number of photons, N600 in the 600 nm beam. Question 5 options: N400 = 2*N600 N400 = 32600 N400 = N600 N400 = 23600 N400 = 2600 None of the other responses are correct.arrow_forward
- When the light of wavelength 250 nm is incident on a metal surface, the maximum speed of the photoelectrons is 4.0 × 105 m/s, what is the work function of the metal in electron-volts?B. Assume that a 100-W light bulb gives off 2.50% of its energy as visible light of wavelength 500 nm. How many photons of visible light are given off in 1.0 min?arrow_forwardThe threshold of dark - adapted (scotopic) vision is 4.0 x 10-11 W/m2 at a central wavelength of 5.00 x 102 nm. If light with this intensity and wavelength enters the eye when the pupil is open to its maximum diameter of 8.5 mm, how many photons per second enter the eye?arrow_forwardThe intensity of sunlight hitting the surface of the earth on a cloudy day is about 0.50 kW/m2. Assuming your pupil can close down to a diameter of 2.0 mm and that the average wavelength of visible light is 550 nm, how many photons per second of visible light enter your eye if you look up at the sky on a cloudy day?arrow_forward
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