An instructor's laser pointer produces a beam of light with a circular cross section of diameter 1.30 mm and an average poweroutput of 8.00 mW. The beam size stays nearly constant when the instructor uses the laser pointer in the classroom.What is the amplitude Eo of the electric field of thelaser's light?Eo=What is the amplitude Bo of the magnetic field of thelaser's light?What is the average energy density wave of the laser's light?N/CBo=TJ/m³Wave

Answered: An instructor's laser pointer produces…

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter16: Electromagnetic Waves

Section: Chapter Questions

Problem 60P: Assume the helium-neon lasers commonly used in student physics laboratories have power outputs of...

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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?
A plane electromagnetic wave of frequency 20 GHz moves in the positive y-axis direction such that its electric field is pointed along the z-axis. The amplitude of the electric field is 10 V/m. The start of time is chosen so that at t = 0, the electric field has a value 10 V/m at the origin. (a) Write the wave function that will describe the electric field wave, (b) Find the wave function that will describe the associated magnetic field wave.
A small helium-neon laser has a power output of 2.5 mW What is the electromagnetic energy in a 1.0-m length of the beam?
Assume the helium-neon lasers commonly used in student physics laboratories have power outputs of 0.500 mW. (a) If such a laser beam is projected onto a circular spot 1.00 mm in diameter, what Is its Intensity? (b) Find the peak magnetic field strength. (C) Find the peak electric field strength.
At the top of Earth’s atmosphere, the time-averaged Porting vector associated with sunlight has a magnitude of about 1.4W/m2 . (a) What are the maximum values of the electric and magnetic fields for a wave of this intensity? (b) What is the total power radiated by the sun? Assume that the Earth is 1.51011m from the Sun and that sunlight is composed of electromagnetic plane waves.
What are the wavelengths of (a) X-rays of frequency 2.01017 Hz? (b) Yellow light of frequency 5.11014Hz ? (C) Gamma rays of frequency 1.01023Hz ?
On its highest power setting, a microwave oven increases the temperature of 0.400 kg of spaghetti by 45.0°C in 120 s. (a) What was the rate of energy absorption by the spaghetti, given that its specific heat is 3.76103J/kg.C ? Assume the spaghetti is perfectly absorbing. (b) Find the average intensity of the microwaves, given that they are absorbed over a circular area 20.0 cm in diameter. (C) What is the peak electric field strength of the microwave? (d) What is its peak magnetic field strength?
Suppose a spherical particle of mass m and radius R in space absorbs light of intensity I for time t. (a) How much work does the radiation pressure do to accelerate the particle (mm rest In the given tine It absorbs the light? (b) How much energy canted by the electromagnetic waves is absorbed by the particle over this time based on the radiant energy incident on the particle?
If plane polarized light is sent through two polarizers, the first at 45 to the original plane of polarization and the second at 90 to the original plane of polarization, what fraction of the original polarized intensity passes through the last polarizer? (a) 0 (b) 14 (c) 12 (d) 18 (e) 110
A particle of cosmic dust has a density =2.0g/cm3 , (a) Assuming the dust particles are spherical and light absorbing, and are at the same distance as Earth from the Sun, determine the particle size for which radiation pressure from sunlight is equal to the Sun's force of gravity on the dust particle, (b) Explain how the forces compare if the particle radius is smaller, (c) Explain what this implies about the sizes of dust particle likely to be present in the inner solar system compared with outside the Oort cloud.
The Poynting vector describes a flow of energy whenever electric and magnetic fields are present. Consider a long cylindrical wire of radius r with a current I in the wire, with resistance R and voltage V. From the expressions for the electric field along the wire and the magnetic field around the wire, obtain the magnitude and direction of the Poynting vector at the surface. Show that it accounts for an energy flow into the wire from the fields around it that accounts for the Ohmic heating of the wire.
A radio station broadcasts its radio waves with a power of 50,000 W. What would be the intensity of this signal if it is received on a planet orbiting Proxima Centuri, the closest star to our Sun, at 4.243 ly away?

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