Electromagnetic Waves AP Physics 2 MCQ – Exam Style Questions etc.
Electromagnetic Waves AP Physics 2 MCQ
Unit 14: Waves , Sound , and Physical Optics
Weightage : 15–18%
Exam Style Practice Questions , Electromagnetic Waves AP Physics 2 MCQ
Question
The figure above represents the electric field \(E\) as a function of position \(x\) due to a particular radio wave at time \(t=0 \mathrm{~s}\). Which of the following equations correctly describes the electric field?
(A) \(E=(100 \mathrm{~N} / \mathrm{C}) \cos \left(\frac{\pi x}{1 \mathrm{~m}}\right)\)
(B) \(E=(100 \mathrm{~N} / \mathrm{C}) \cos \left(\frac{\pi x}{2 \mathrm{~m}}\right)\)
(C) \(E=(100 \mathrm{~N} / \mathrm{C}) \cos \left(\frac{\pi x}{4 \mathrm{~m}}\right)\)
(D) \(E=(100 \mathrm{~N} / \mathrm{C}) \sin \left(\frac{\pi x}{4 \mathrm{~m}}\right)\)
▶️Answer/Explanation
Ans: C
Questions
The figure above shows a model of an electromagnetic wave, where E is the electric field and B is the magnetic field. In what direction is the energy of the wave transmitted?
(A) Along the x-axis only
(B) Along the y-axis only
(C) Along the z-axis only
(D) In a direction that is at a nonzero angle to each of the axes
▶️Answer/Explanation
Ans: A
This option is correct. Electromagnetic waves, like waves on a string, are transverse: the direction of the “disturbance” is perpendicular to the direction in which the waves travel, i.e., the direction in which energy is transmitted. Here, the electric and magnetic “disturbances” are y-directed and z-directed; therefore the waves must be traveling perpendicular to both of those transverse disturbances, along the x-axis.
Question
You and a friend are traveling in a car. You tune the car radio to a station of frequency 850 kHz. The graph below represents the electric field strength of the radio wave at a given position as a function of time.
Which of the following best represents the electric field strength E measured in V/m as a function of time t measured in \(\mu s\)?
(A) \(E=(3.0\times 10^{-4})\sin (10.6t)\)
(B) \(E=(3.0\times 10^{-4})\sin (5.32t)\)
(C) \(E=(1.5\times 10^{-4})\sin (10.6t)\)
(D) \(E=(1.5\times 10^{-4})\sin (5.32t)\)
Answer/Explanation
Ans:D