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Exam 31: Electromagnetic Waves

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Question 21

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A monochromatic point like light source emits 1.50 W of electromagnetic power uniformly in all directions.The Poynting vector in a point situated at 0.750 m from the source is

A) 0.212 W/m².
B) 0.119 W/m².
C) 0.367 W/m².
D) 0.0578 W/m².
E) 0.437 W/m².

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Question 22

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Which four quantities do Maxwell's Equations relate to each other?

A) electric field,capacitance,resistance,and inductance
B) electric field,charge,current,and voltage
C) electric field,magnetic field,charge,and current
D) electric field,magnetic field,energy,and power

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Question 23

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What is the electric field amplitude of an electromagnetic wave whose magnetic field amplitude is 5 * 10^-3 T?

A parallel plate capacitor with circular plates of radius 10.0 cm are separated by a distance of 5.0 mm.The potential across the capacitor is increased at a constant rate of 120 V/s.Find the distance from the center of the plates,outside of the space between the plates (r >10cm) where the magnetic field is 3.6 * 10^-15 T.

A cell phone transmits 2.0 W of power at 380 MHz in a spherical pattern.What is the intensity of the radiation at the cell tower,located 3.0 km away?

Which waves travel fastest in vacuum?

A 10-mW vertically polarized laser beam passes through a polarizing filter whose axis is 30 degrees from the horizontal followed by another polarizing filter with its axis horizontal.What is the power in the laser beam that emerges from the polarizer?

Sunlight is coming straight down on a solar panel (length 1.25 m and width W=0.850 m) belonging to the Spirit Mars rover.The amplitude of the electric field in the solar radiation is 642 V/m and is uniform (the radiation has the same amplitude everywhere) .If the solar panel has an efficiency of 20.4 percent in converting solar radiation into electrical power,how much average power can the panel generate from the solar radiation?

Unpolarized light of intensity 100 mW/m² passes through two filters.The first filter has an alignment of 30.0 degrees from the vertical.The intensity of the light that passes through the second filter is 41 mW/m². What is the angular alignment of the second filter with respect to the vertical?

A monochromatic point like light source emits 1.50 W of electromagnetic power uniformly in all directions.How far from the point source is the Poynting vector 0.367 W/m²?

Which waves have the highest frequency in the electromagnetic spectrum?

A monochromatic point like light source emits electromagnetic power uniformly in all directions.The Poynting vector in a point situated at 0.500 m from the source is 0.375 W/m².The power of the source is

In outer space,there are two astronauts at rest,one 20.0 m from the space shuttle and the other 40.0 m away from the shuttle.By using a 20-W laser,the astronaut located 40.0 m away from the shuttle decides to propel the other astronaut towards the space shuttle.He focuses the laser on a piece of totally reflecting fabric on her space suit.If her total mass with equipment is 100 kg,what is her acceleration towards the shuttle?

A small,perfectly reflecting Mylar disc,density 1.1 g/cm³,radius 0.15 mm,thickness 0.050 mm,is levitated by a laser,whose beam at the point of interaction of beam and disc is 0.35 mm in diameter.Assuming the disc is levitating in a horizontal orientation,what power does the laser emit?

A parallel plate capacitor with circular plates of radius 10.0 cm are separated by a distance of 5.0 mm.The potential across the capacitor is increased at a constant rate.If the magnitude of the magnetic field between the plates at a distance r = 1.0 cm from the center is 3.6 * 10^-15 T,what is the rate of increase in the potential across the plates of the capacitor?

There are two polarizing filters that are out of alignment by 30 degrees.If light of intensity 1.00 W/m² and initially polarized half-way between the two filters passes through the two filters,what is the intensity of the transmitted light?

At a certain instant in time,in an electromagnetic wave,the electric field vector points to the north and the magnetic field vector points vertically downward.In which direction is the electromagnetic wave moving?

An industrial CO₂ laser produces a beam of radiation with average power of 5.60 kW at a wavelength of 10.6 $\mu$ m.Such a laser can be used to cut steel up to 25 mm thick! The laser light is polarized in the x-direction,travels in the positive z-direction,and is collimated (neither diverging or converging) at a constant diameter of 148 $\mu$ m.The laser light is completely absorbed by small spherical dust particle with diameter of 50 $\mu$ m.What is the force that the laser beam exerts on the dust particle (before it is incinerated!) ?

The potential across a capacitor is increasing at a rate of 120 V/s.If the displacement current through the capacitor is 10.0 A,what is the capacitance of the capacitor?

Point out the incorrect statement with respect to an electromagnetic wave in vacuum (or air) .