25.3.2—Redshift of electromagnetic radiation

use ∆λ / λ ≈ ∆f / f ≈ v / c for the redshift of electromagnetic radiation from a source moving relative to an observer.

Use —redshift of electromagnetic radiation to connect the rule to the data and decision in the question.

This matters because —redshift of electromagnetic radiation determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —redshift of electromagnetic radiation to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Redshift of electromagnetic radiation is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.