{"uid":"cap_tiU0R7s_U9Fll7_nAhHXU","slug":"physics-calculators-wave-speed-frequency-wavelength-doppler-shift-d0ccd6f3","name":"Physics Calculators: Wave Speed, Frequency, Wavelength & Doppler Shift","description":"Wave speed, frequency and wavelength, plus the Doppler-shifted frequency for sound (moving source or observer) or light.","url":"https://physics-calc.x402tookit.com/wave-doppler?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["frequencyHz"],"properties":{"medium":{"type":"string","description":"sound (default, in air) or light"},"airTempC":{"type":"number","description":"Air temperature in C for the speed of sound, -50 to 60 (default 20)"},"frequencyHz":{"type":"number","description":"Source frequency in Hz"},"wavelengthM":{"type":"number","description":"Wavelength in metres, to get wave speed"},"sourceSpeedMS":{"type":"number","description":"Source speed in m/s, positive toward the observer, negative away (sound)"},"observerSpeedMS":{"type":"number","description":"Observer speed in m/s, positive toward the source (sound)"},"closingSpeedFractionOfC":{"type":"number","description":"Light: closing speed as a fraction of c, -0.999 to 0.999 (positive = approaching)"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"source":{"type":["null","string"]},"formula":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"airTempC":{"type":["null","number"]},"degraded":{"type":["boolean","null"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"frequencyHz":{"type":["null","number"]},"dopplerFactor":{"type":["null","number"]},"speedOfSoundMS":{"type":["null","number"]},"observedFrequencyHz":{"type":["null","number"]}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_o5A27lTp3WanQImqeered","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates wave speed, frequency, and wavelength relationships, plus Doppler-shifted frequency for sound (moving source or observer) or light (relativistic).","exampleAgentPrompt":"A police siren emits sound at 800 Hz and the car is moving toward me at 40 m/s — the air temperature is 25°C. What frequency do I actually hear?","exampleUseCases":[{"title":"Ambulance siren frequency shift","prompt":"An ambulance siren is 700 Hz and it's approaching me at 25 m/s on a 20°C day. What frequency do I hear, and what's the formula behind it?"},{"title":"Relativistic Doppler for approaching star","prompt":"A star is approaching Earth at 0.3 times the speed of light and emits light at 600 nm (that's about 500 THz). What frequency does an observer on Earth detect?"},{"title":"Wavelength of a sound wave","prompt":"What is the wavelength of a 440 Hz sound wave in air at 15°C? Also tell me the wave speed used."}],"resultDescription":"Returns the observed (Doppler-shifted) frequency in Hz, the Doppler factor, speed of sound in m/s (for sound), the air temperature used, the formula applied, a plain-English summary of the result, and any relevant disclaimers or degradation flags.","failureModes":["Missing required frequencyHz parameter returns an error","Air temperature out of range (-50 to 60°C) may return a validation error","Closing speed fraction of c outside -0.999 to 0.999 returns an error for light","Invalid medium value (not 'sound' or 'light') may cause unexpected behavior","Providing both sourceSpeedMS and closingSpeedFractionOfC for the wrong medium may yield incorrect results"],"whenToPreferThis":"Choose this endpoint when you need precise Doppler shift calculations for either sound or light, including temperature-adjusted speed of sound, moving-source or moving-observer scenarios for acoustics, or relativistic Doppler for light. It covers wave speed and wavelength relationships in the same call. Prefer it over general physics APIs when you need the Doppler factor and formula explanation alongside the numeric result.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-30T00:35:04.158Z","isFirstParty":false,"canonicalSlug":"physics-calculators-wave-speed-frequency-wavelength-doppler-shift-d0ccd6f3"}