Wave properties — wavelength, frequency, amplitude — and how they explain reflection, refraction, and pitch. Nearly every calculation here comes back to one equation: wave speed equals wavelength times frequency. Every question comes with a written walkthrough of the relationship used.
Amplitude measures a wave's height (its energy or intensity), while wavelength measures the distance between repeating points — changing one doesn't necessarily change the other.
When a wave enters a new medium, its speed and wavelength change, but its frequency stays fixed — frequency is set by the source that created the wave, not by whatever medium it's currently traveling through.
In a transverse wave the particles move perpendicular to the wave's travel direction; in a longitudinal wave they move parallel to it, compressing and expanding — sound is longitudinal even though it's often drawn as a transverse-looking squiggle for simplicity.
Straight from the bank — one per difficulty tier. Reveal the answer to see the explanation you'd get in a real session.
A wave has a frequency of 5 Hz and a wavelength of 2 meters. What is its speed?
A — 10 m/s. Wave speed equals frequency times wavelength: v = fλ = (5)(2) = 10 m/s. 2.5 m/s (B) comes from dividing instead of multiplying — computing 5/2 instead of 5×2.
A sound wave travels from air into water, where it speeds up significantly. What happens to its frequency and wavelength?
A — Frequency stays the same; wavelength increases. Frequency is determined by the source producing the wave and doesn't change when the wave enters a new medium. Since v = fλ and the speed increased while frequency stayed fixed, the wavelength must increase to keep the equation balanced. Frequency stays the same; wavelength decreases (D) gets the frequency right but has the wavelength relationship backward — wavelength moves in the same direction as speed when frequency is constant, not the opposite direction.
A wave traveling at 340 m/s has a wavelength of 0.85 m. If the wave's frequency is doubled while its speed stays the same, what is the new wavelength?
A — 0.425 m. The original frequency is f = v/λ = 340/0.85 = 400 Hz. Doubling it gives 800 Hz. Since speed stays constant, the new wavelength is λ = v/f = 340/800 = 0.425 m — exactly half the original, since wavelength and frequency are inversely related at a fixed speed. 1.7 m (B) comes from doubling the wavelength instead of halving it, treating frequency and wavelength as directly proportional instead of inversely proportional.
Wave problems reward knowing which quantity stays fixed when a wave changes medium — frequency is set by the source and never changes, which is the one fact most of these questions hinge on.
For every wave problem, name whether frequency, wavelength, or speed is fixed before applying v = fλ. Untimed practice is where that identification gets fast.
Move to timed sessions once the wave-speed equation and its inverse relationships are instant recall.
Pair waves, light, and sound with electricity and magnetism in a mock — light itself is an electromagnetic wave connecting the two subtopics directly.
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