Electromagnetic Waves - Questions

Electromagnetic Waves
































Maxwell's theory of electromagnetism predicted that electromagnetic waves in vacuum propagate at m/s relative to

(A) a reference frame in which the usual laws of mechanics work.
(B) a reference frame in which the usual laws of electricity and magnetism work.
(C) the luminiferous aether.
(D) their source.

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Maxwell's theory of electromagnetism predicted that electromagnetic waves in vacuum propagate at m/s relative to

(A) a reference frame in which the usual laws of mechanics work.

No. --- That is actually right, but it is not what Maxwell predicted.


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Maxwell's theory of electromagnetism predicted that electromagnetic waves in vacuum propagate at m/s relative to

(B) a reference frame in which the usual laws of electricity and magnetism work.

Yes. --- The speed follows directly from those laws.


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Maxwell's theory of electromagnetism predicted that electromagnetic waves in vacuum propagate at m/s relative to

(C) the luminiferous aether. --- No.

Some physicists of the time thought that, but they were wrong.


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Maxwell's theory of electromagnetism predicted that electromagnetic waves in vacuum propagate at m/s relative to

(D) their source. --- No.

There were physicists who thought that, but they were wrong.


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The first demonstration of electromagnetic wave generation used

(A) electric sparks in air.
(B) vacuum tube oscillators.
(C) charged mechanical rotors.
(D) rapid mechanical switches.


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The first demonstration of electromagnetic wave generation used

(A) electric sparks in air. --- Yes.

Spark gaps hooked to antennas
were the first radio transmitters.

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The first demonstration of electromagnetic wave generation used

(B) vacuum tube oscillators. --- No.

They are a relatively recent invention.


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The first demonstration of electromagnetic wave generation used

(C) charged mechanical rotors. --- No.

They could not spin fast enough
or hold enough charge.

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The first demonstration of electromagnetic wave generation used

(D) rapid mechanical switches. --- No.

They were not fast enough
to generate the oscillations.

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Electromagnetic waves propagate

(A) only where there are charged particles.
(B) only in air or water.
(C) through anything at all.
(D) through a vacuum.



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Electromagnetic waves propagate

(A) only where there are charged particles.

No. Charged particles can generate waves
but the waves can travel where there are
no charged particles.


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Electromagnetic waves propagate

(B) only in air or water. --- No.

Actually these substances absorb them a bit.



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Electromagnetic waves propagate

(C) through anything at all. --- No.

Many substances absorb them.



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Electromagnetic waves propagate

(D) through a vacuum. --- Yes.

The fields maintain themselves.



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Which of the following phenomena consist of electromagnetic waves travelling at the speed of light:

(A) sound. ------ (B) X-rays.

(C) beta rays. --- (D) alpha rays.


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Which of the following phenomena consist of electromagnetic waves travelling at the speed of light:

(A) sound. --- No.

That consists of waves in air,
travelling much slower than light.

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Which of the following phenomena consist of electromagnetic waves travelling at the speed of light:

(B) X-rays. --- Yes.

They are very short wavelength
electromagnetic waves.

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Which of the following phenomena consist of electromagnetic waves travelling at the speed of light:

(C) beta rays. --- No.

We have not discussed those yet.
They are particles moving slower than light.

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Which of the following phenomena consist of electromagnetic waves travelling at the speed of light:

(D) alpha rays. --- No.

We have not discussed those yet.
They are particles moving slower than light.

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