19 If we plot a graph between frequency of light used and maximum K.E of photoelectrons it will be a straight line intercepting frequency axis at one point. The intercepting point depends upon * Frequency of incident light The number of ejected electrons. Material used in photo emissive surface Voltage applied between two plates

19 If we plot a graph between frequency of light used and maximum K.E of photoelectrons it will be a straight line intercepting frequency axis at one point. The intercepting point depends upon * Frequency of incident light The number of ejected electrons. Material used in photo emissive surface Voltage applied between two plates

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter24: Electromagnetic Waves

Section: Chapter Questions

Problem 22CQ: Laser vision correction often uses an excimer laser that produces 193-nm electromagnetic radiation....

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Why don't we notice quantization in everyday events?
Laser vision correction often uses an excimer laser that produces 193-nm electromagnetic radiation. This wavelength is extremer strongly absorbed by the cornea and athletes it in a manner that reshapes the cornea to correct vision detects. Explain how the strong absorption helps concentrate the energy in a thin layer and thus give greater accuracy in shaping the cornea. Also explain how this strong absorption limits damage to the lens and retina of the eye.
Consider a 250-W heat lamp fixed to the ceiling in a bathroom. If the filament in one light burns out then the remaining three still work. Construct a problem in which you determine the resistance of each filament in order to obtain a certain intensity projected on the bathroom floor. The ceiling is 3.0 m high. The problem will need to involve concave miners behind the filaments. Your instructor may wish to guide you on the level of complexity to consider in the electrical components.
A circular radar antenna on a Coast Guard ship has a diameter of 2.10 m and radiates at a frequency of 15.0 GHz. Two small boats are located 9.00 km away from the ship. How close together could the boats he and still he detected as two objects?
Lunar astronauts placed a reflector on the Moon’s surface, off which a laser beam is periodically reflected. The distance to the Moon is calculated from the round-trip time. (a) To what accuracy in meters can the distance to the Moon be determined, If this time can be measured to 0.100 ns? (b) What percent accuracy is this, given the average distance to the Moon is 384,480 kin?
Suppose a star 1000 times brighter than our Sun (that is, emitting 1000 times the power) suddenly goes supernova. Using data from Table 7.3: (a) By what factor does its power output increase? (b) How many times brighter than our entire Milky Way galaxy is the supernova? (c) Based on your answers, discuss whether it should be possible to observe supernovas in distant galaxies. Note that there are on the order of 1011 observable galaxies, the average brightness of which is somewhat less than our own galaxy.
Your pupils dilate when visible light intensity is reduced. Does wearing sunglasses that lack UV blockers increase or decrease the UV hazard to your eyes? Explain.
Oxygenated hemoglobin absorbs weakly in the red (hence its red color) and strongly in the near infrared, whereas deoxygenated hemoglobin has the opposite absorption. This fact is used in a pulse oximeter to measure oxygen saturation in arterial blood. The device clips onto the end of a persons finger and has two light-emitting diodesa red (660. nm) and an infrared (940. nm)and a photocell that detects the amount of light transmitted through the linger at each wavelength. (a) Determine the frequency of each of these light sources. (b) If 67% of the energy of the red source is absorbed in the blood, by what factor does the amplitude of the electromagnetic wave change? Hint: The intensity of the wave is equal to the average power per unit area as given by Equation 21.28.
Radio station WWVB, operated by the National Institute of Standards and Technology (NIST) from Fort Collins, Colorado, at a low frequency of 60 kHz, broadcasts a time synchronization signal whose range covers the entire continental US. The timing of the synchronization signal is controlled by a set of atomic clocks to an accuracy of 101012 s, and repeats every 1 minute. The signal is used for devices, such as radio-controlled watches, that automatically synchronize with it at preset local times. WWVB's long wavelength signal tends to propagate close to the ground. (a) Calculate the wavelength of the radio waves from WWVB. (b) Estimate the error that the travel time of the signal causes in synchronizing a radio controlled watch in Norfolk, Virginia, which is 1570 mi (2527 km) from Fort Collins, Colorado.
Problem 7: If you wish to observe features that are around the size of atoms, say 8.5 × 10-10 m, with electromagnetic radiation, the radiation must have a wavelength of about the size of the atom itself. Part (a) If you had a microscope which was capable of doing this, what would the frequency of electromagnetic radiation be, in hertz, that you would have to use? Part (b) What type of electromagnetic radiation would this be? Infrared Gamma rays None of these UltravioletX-Rays
Pulsed lasers used in science and medicine produce very short bursts of electromagnetic energy. If the laser light wavelength is 1062 nmnm (Neodymium-YAG laser), and the pulse lasts for 35 picoseconds, how many wavelengths are found within the laser pulse? Assume that the wave travels in free space. Express your answer using two significant figures. How brief would the pulse need to be to fit only one wavelength? Express your answer to three significant figures and include the appropriate units.
You are working as a demonstration assistant for a physics professor. She wants to demonstrate to her students the buildup of the interference pattern for single electrons passing through a double slit. Her source of electrons will be a certain vacuum tube, in which electrons evaporate from a hot cathode at a slow, steady rate and accelerate from rest through a potential difference of 45.0 V. After being accelerated, they travel through a fieldfree and evacuated region before they pass through the double slits and fall on a screen to produce an interference pattern. To ensure that only one electron at a time is passing through the slits, she wants the electrons to be separated in space by d 5 1.00 cm (perpendicular to the barrier containing the slits) as they approach the slit. She asks you to determine the maximum value for the beam current that will assure that only one electron at a time passes through the slits.