32. Electromagnetic Waves

Intro to Electromagnetic (EM) Waves

Multiple Choice
Which of the following is a key difference between electromagnetic waves and mechanical waves?
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Multiple Choice
For an electromagnetic wave traveling in vacuum, what happens to the frequency $f$ as the wavelength $λ$ increases, given $c = f λ$ ?
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Multiple Choice
Which of the following best describes a key difference between electromagnetic waves and mechanical waves?
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Multiple Choice
In introductory electromagnetism, what is the physical source of an electromagnetic wave in free space?
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Multiple Choice
In the context of electromagnetic waves, increasing the number of loops in a coil will increase the $m a g n i t u d e$ of the magnetic field produced by the coil. Which property does this refer to?
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Multiple Choice
Which of the following best describes a key difference between electromagnetic waves and mechanical waves?
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Multiple Choice
Which of the following statements is true about electromagnetic waves propagating in air?
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Multiple Choice
A $50 W$ lightbulb emits light uniformly in all directions. What is the electric field amplitude $10 cm$ away from the lightbulb?
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Multiple Choice
What is the magnetic field amplitude of an electromagnetic wave that has electric field amplitude $1500 V/m$ ?
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Multiple Choice
Alice observes an electric field, $\overset{⇀}{E} = (30 \frac{V}{m}) \hat{k}$ , and a magnetic field $\overset{⇀}{B} = (0.10 T) \hat{i}$ . Bob is cruising by, with velocity $\overset{⇀}{v} = (100 \frac{m}{s}) \hat{j}$ , in Alice's reference frame. What electric field does Bob observe?
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Multiple Choice
You measure the electric field of an electromagnetic wave at a particular moment and find it points in the +z direction. The magnetic field points in the +y direction. In which direction is this wave traveling?
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Multiple Choice
Which statement correctly describes a key difference between a radio wave and a sound wave?
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Multiple Choice
You measure the magnetic field strength of a traveling electromagnetic wave to be $8.0$\times$10^{-7}T$ , oriented along the +x direction. If this EM wave moves in the +y direction, what is the magnitude and direction of the wave's electric field at that same exact spot?
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Multiple Choice
The equation for the electric field in an electromagnetic wave is given by E_max*cos(ky + wt). What is the direction of propagation of this wave?
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