Q264 · Practice questionSimple familiar2 marks
QUESTION 264 (2 marks)
An antenna charge oscillates vertically. At a distant point, the electromagnetic wave travels horizontally to the right and its electric field is momentarily vertically upward.
a)[2 marks]
Describe how oscillating charges generate electromagnetic waves, and give the orientation of the magnetic field relative to the electric field and propagation direction.
WORKED SOLUTION
2 marksPractice marking scheme
ANSWER
(a) Accelerated oscillating charges produce changing electric and magnetic fields that propagate; the magnetic field is perpendicular to both the electric field and propagation direction.
Worked solution
(a) The wave contains coupled oscillating electric and magnetic fields. Both are transverse to propagation and mutually perpendicular. For rightward propagation and upward electric field, the magnetic field is out of the page.
Equivalent physically justified methods, alternative valid sketches and consistent units accepted.
Accept sensible significant figures and consistent rounding from stated constants.
Part a: Connect oscillating accelerated charges with propagating changing fields.
Part a: State mutually perpendicular electric/magnetic fields, both transverse to propagation.
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