IB Physics SL C.2.5 Electromagnetic Wave Speed

Practise applying c = fλ to electromagnetic radiation in vacuum and explaining how frequency remains fixed while speed and wavelength change when light enters a material.

Exam points

use c = 3.00 × 10⁸ m s⁻¹ with vacuum frequency and wavelength in consistent SI units
keep frequency unchanged at a boundary while calculating lower speed and wavelength in a medium
connect refractive index to wave speed with n = c/v without applying c inside the material

[Maximum number: 1]

A rocket moving with speed v relative to the ground emits a flash of light in the backward direction.

Figure for Question C.2.5—Electromagnetic wave speed question 1 — IB Physics SL

An observer in the rocket measures the speed of the flash of light to be c.
State the speed of the flash of light according to an observer on the ground using

Maxwell's theory of electromagnetism.

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C.2.5—Electromagnetic wave speed question 1