How It Works: Why Speed Changes at Boundaries
Part of Wave Properties — GCSE Physics
This how it works covers How It Works: Why Speed Changes at Boundaries within Wave Properties for GCSE Physics. Revise Wave Properties in Waves for GCSE Physics with 21 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 6 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 6 of 13
Practice
21 questions
Recall
15 flashcards
⚙️ How It Works: Why Speed Changes at Boundaries
When a wave moves from one medium to another (e.g., light entering glass from air), its speed changes because the particles or fields in the new medium respond differently. Crucially, the frequency stays the same — it is determined by the source, not the medium. Since v = f × λ and f is fixed, a change in speed must produce a change in wavelength.
If speed decreases (entering a denser medium), wavelength gets shorter. If speed increases (leaving a denser medium), wavelength gets longer. This is the foundation for understanding refraction — a wave slowing down also changes direction unless it hits the boundary at 90°.