Chapter 22 electromagnetic waves
The electric field E and the magnetic field B in an electromagnetic wave have the same frequency and wavelength and oscillate through maximum E and maximum B at the same point and time, so they are _____.
in phase
The sinusoidal electromagnetic plane wave may be described by a set of sinusoidal wave functions of amplitude E0 and B0 for the electric and magnetic fields, respectively. The units of E0 are newtons per coulomb (N/C), or equivalently volts per _____ .
meter, V/m
One of Maxwell's equations is Gauss's law written as ΦB = 0. If ΦB were found to be non-zero it would be evidence of the existence of _____. No such observation has ever been confirmed.
monopoles
Although an electromagnetic wave does not require a medium through which to travel, the relationship to the propagation speed is the same as in mechanical waves, where the frequency of the wave (f) _____ (λ) equals the speed of propagation of the wave
multiplied by the wavelength
The energy of a photon is proportional to ________.
Its frequency
Maxwell Equations 1
Gaussian surface
The _____ is the name given to the full range of possible electromagnetic waves, from very low frequency radio waves to very high frequency gamma rays. Since c = fλ for any electromagnetic wave traveling in a vacuum, this can be described in terms of the range of possible _____ equally well. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices
electromagnetic spectrum, wavelength
Gauss's law written as ΦE = (1/ε0)qencl is _____. A hypothetical longitudinal electromagnetic wave (which carries no charge, so ΦE must be zero) violates Gauss's law. This leads to the conclusion that electromagnetic waves must be transverse, with the varying electric field vector _____ the direction of propagation.
one of maxwell's equations; perpendicular to
The energy of an electromagnetic wave propagates as small, individual packets called _____, and the energy of each packet is proportional to the wave frequency.
photons
sinusoidal electromagnetic plane wave
the electric and magnetic fields both oscillate in phase with the same wavelength and frequency, The field directions are perpendicular to each other and perpendicular to the direction of propagation.
Maxwell Equations 3
ampere law
The amplitude of the electric and magnetic fields in electromagnetic waves affects the waves' ________.
average intensity
A parallel plate capacitor is being charged by current 𝒾 as shown in the figure, causing an increasing, upward electric field between the plates. The magnetic field produced around the loop shown (looking down upon the loop) is _______.
counter clockwise
An electromagnetic wave carries energy that is stored _____. The wave functions that describe the electromagnetic wave vary with time and location, but on average the electric energy density _____ the magnetic energy density
in its oscillating electric and magnetic fields; is equal to
One of Maxwell's equations is Faraday's law, ε = -ΔΦB/Δt. Faraday's law states that an emf (ε) is induced in a loop if the _____ through that loop changes, and that the induced current will be in the direction that would induce a field _____ the change in flux.
magnetic flux; opposing
electromagnetic waves
waves that re propagated by the simultaneous periodic variations of electric and magnetic fields. These include radio waves, infrared, visible light, ultraviolet, x rays, and gamma rays.
Electromagnetic plane waves
The simplest electromagnetic waves in a vacuum is a sinusoidal plane wave. The electric and magnetic fields oscillate in phase, are perpendicular to each other, and are transverse (both are perpendicular to the direction of wave propagation. The ap
Maxwell's Equations
a set of four fundamental laws expressed in mathematical form that govern electricity and magnetism and their interrelationship.
Faraday's law holds even if there is no conducting material present to carry an induced current, in which case it may be stated in terms of the _____around a loop instead of the induced emf. This gives ΣE||Δℓ = -ΔΦB/Δt, where E|| is the component of the electric field tangent to the loop and Δℓ is a small increment of length around the loop. The loop need not be a material substance.
circulating electric field
It is useful to think of an electric field as stored energy and to define the _____ as equal to _____ where E is the electric field magnitude.
electric energy density; ½ε0E2
One of Maxwell's equations is Gauss's law written as ΦE = (1/ε0)qencl. ΦE is written with a subscript to highlight that this equation is specifically addressing _____ across a closed surface. Please choose the correct answer from the following choices, and then select the submit answer button. Answer choices
electric flux
There is a broad variety of _____ waves, but unlike sound waves or waves in water, this type of wave involves _____ electric and magnetic fields and requires no physical medium through which to propagate.
electromagnetic; oscillating
The electric energy stored in a capacitor can be thought of as stored in its electric field, which is largely restricted to the space between the plates. This motivates defining the energy per unit volume due to an electric field, or electric _____
energy density
A wire loop is placed between the poles of an electromagnet whose magnetic field B is pointing up as shown in the figure. An emf ε is induced in the wire loop that causes current to flow clockwise as indicated by the arrows shown. By considering Lenz's law it may be concluded that the magnetic field is _____.
increasing
Which of the following is a true statement concerning the propagation of light?
light does not require any medium to propagate
One of Maxwell's equations is Faraday's law, ε = -ΔΦB/Δt. Faraday's law states that an emf is induced in a loop if the _____through that loop changes.
magnetic flux
One kind of electromagnetic wave is the sinusoidal plane wave, a(n) _____ that is relatively simple to analyze, with electric and magnetic fields that _____.
mathematical idealization
The electric field E and the magnetic field B in an electromagnetic wave are _____, but both oscillate with the same frequency and wavelength and are _____.
mutually perpendicular; in phase
The electric field E and the magnetic field B vary _____ the direction of propagation, so electromagnetic waves are transverse. Additionally, the E vector and the B vector are _____.
perpendicularly to the; perpendicular to each other
A useful way to express the energy carried by an electromagnetic wave is in terms of the wave intensity, or average _____ per unit area.
power
The energy of an individual photon is directly proportional to the _____, and the proportionality constant is called _____ constant h = 6.63 × 10-34 J·s.
wave frequency; Planck's
Select the statement that contradicts one of Maxwell's equations.
The net magnetic flux through a closed surface depends on the current inside.
The Maxwell-Ampere law, ΣB||Δℓ = μ0(𝒾through + ε0ΔΦE/Δt), states that a circulating magnetic field is produced around a loop by a current that the loop encircles (the 𝒾through term) or a time-varying electric flux through the loop. The latter is the ε0ΔΦE/Δt term, also known as the _____.
displacement current
Gauss's law written as ΦE = (1/ε0)qencl is one of Maxwell's equations. A hypothetical longitudinal electromagnetic wave (which carries no charge, so ΦE must be zero) violates Gauss's law. This leads to the conclusion that electromagnetic waves must be _____
inverse
Maxwell Equations
Faradays law and lenz's law of inductions
Maxwell Equations 2
Farradays law in terms of circulation
speed of electromagnetic waves
In a vacuum all electromagnetic waves propagate at the same speed c = 3.00 x 10^8 m/s. The shorter the wavelength, the higher the frequency of the wave. Our eyes are sensitive to only a narrow band of wavelengths known as the visible spectrum.
The sinusoidal electromagnetic plane wave may be described by a set of sinusoidal wave functions of amplitude E0 and B0 for the electric and magnetic fields, respectively. The units of B0 are (N·s)/(C·m), or equivalently the _____.
Tesla, T
Photons
The energy of an electromagnetic waves comes in packets called photons that have properties of both wave and particle. The higher the wave frequency the more energy there is per photon.
speed of light
3.00 x 10^8 m/s
The signal from a 1590 kilohertz AM radio station has a wavelength of approximately _____ meters
190
