https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/mechanical-waves/v/introduction-to-waves 2024-06-20T21:38:16.009746376Z Introduction to waves Transverse and longitudinal waves are two types of mechanical waves, which involve the transfer of energy through a medium (e.g. water, air, a solid). Learn about transverse and longitudinal waves through the examples of a rope and a sound wave. Explore the difference between a single wave pulse and periodic waves. Sal Khan video https://cdn.kastatic.org/googleusercontent/tduQqKFS-v4-zx2ooHTRHNHoMslDaD_H6Rk6w8VuTV-q-9JjphysjBbxOHLbeqe5fqv29PsEarg41QuqEvVFTh1A Introduction to waves Transverse and longitudinal waves are two types of mechanical waves, which involve the transfer of energy through a medium (e.g. water, air, a solid). Learn about transverse and longitudinal waves through the examples of a rope and a sound wave. Explore the difference between a single wave pulse and periodic waves. https://cdn.kastatic.org/ka-youtube-converted/c38H6UKt3_I.mp4/c38H6UKt3_I.mp4 783 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-properties/e/transverse-and-longitudinal-wave-exercises-ap1 2026-04-07T23:55:07.30621384Z Identifying transverse and longitudinal waves Practice identifying representations of transverse and longitudinal waves April Russell exercise https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/mechanical-waves/v/amplitude-period-frequency-and-wavelength-of-periodic-waves 2024-06-20T21:38:16.009746376Z Properties of periodic waves Learn about different properties of waves, including amplitude, period, frequency, and wavelength. Explore how these properties are related to one another. Sal Khan video https://cdn.kastatic.org/googleusercontent/s_Na9kX6xEcMAoiiar-zVOSUj6Ow8e_Q8VuBD8R0KRu0Do4FrdYAJN4Q_b2yvtYLFB3-C0EI6kGEc501ICpQKH5_ Properties of periodic waves Learn about different properties of waves, including amplitude, period, frequency, and wavelength. Explore how these properties are related to one another. https://cdn.kastatic.org/ka-youtube-converted/tJW_a6JeXD8.mp4/tJW_a6JeXD8.mp4 866 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-properties/e/wave-characteristics-ap1 2026-04-07T23:36:17.218592739Z Properties of transverse and longitudinal waves Practice identifying the characteristics of a transverse or longitudinal wave such as the wavelength, crest, and areas of compression. April Russell exercise https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-properties/e/numerical-wave-equation-ap1 2024-06-28T19:56:50.217380579Z Calculating wave speed, frequency, and wavelength Practice using the wave speed equation for word problems to find the frequency and wavelength of a wave.  April Russell exercise https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-properties/e/graphical-wave-equation-ap1 2026-04-07T22:59:30.107127435Z Calculating frequency and wavelength from displacement graphs Practice using a displacement graph and wave speed to find the frequency and wavelength of a wave.  April Russell exercise https://www.khanacademy.org/science/in-in-class11th-physics/in-in-11th-physics-waves/in-in-wave-characteristics/e/wave-energy-ap-physics-1 2026-04-08T00:16:02.937952483Z Wave energy from graphs Practice comparing the energy of waves and wave pulses with different amplitudes, frequencies, wavelengths, and shapes.  Sean exercise https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/mechanical-waves/v/wave-equation 2021-03-21T11:26:13Z The equation of a wave In this video David shows how to determine the equation of a wave, how that equation works, and what the equation represents. David SantoPietro video https://cdn.kastatic.org/googleusercontent/9bsAWY6ndsiGuMEU6_h4jBc_HqZTXojP12WTaqgmVoFQ9DZFSFXp32Lf_jVmyM7m1IIQYDldo6lazfTddgsAYJtq The equation of a wave In this video David shows how to determine the equation of a wave, how that equation works, and what the equation represents. https://cdn.kastatic.org/ka-youtube-converted/9WZM68aVnGk.mp4/9WZM68aVnGk.mp4 884 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-behaviors/e/wave-interference-ap-physics-1 2026-04-07T23:36:17.218592739Z Predicting wave interference patterns Practice predicting how two wave pulses interfere to form new wave patterns as they pass through each other. Sean exercise https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/standing-waves/v/constructive-and-destructive-interference 2024-06-22T14:02:12.128804105Z Constructive and destructive interference Constructive interference happens when two waves overlap in such a way that they combine to create a larger wave. Destructive interference happens when two waves overlap in such a way that they cancel each other out. Wave interference also depends on the relative phase of the two waves, as this video shows through the examples of path length differences and pi shifts. David SantoPietro video https://cdn.kastatic.org/googleusercontent/ue4DKoFZ-8dXABMTqjtB4zoDqrJjz8ne2iT-ixFxxOQxJ2yWZzL14aFjytl-LCVedBbqmxh1xTcQ8dEnBvHjUMeDuw Constructive and destructive interference Constructive interference happens when two waves overlap in such a way that they combine to create a larger wave. Destructive interference happens when two waves overlap in such a way that they cancel each other out. Wave interference also depends on the relative phase of the two waves, as this video shows through the examples of path length differences and pi shifts. https://cdn.kastatic.org/ka-youtube-converted/oTjTXS40pqs.mp4/oTjTXS40pqs.mp4 824 Waves https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/standing-waves/v/standing-waves-on-strings 2024-06-20T21:38:16.009746376Z Standing waves on strings A standing wave occurs when two waves of the same frequency and amplitude are moving in opposite directions and interfere with each other. It has certain points (called nodes) where the amplitude is always zero, and other points (called antinodes) where the amplitude fluctuates with maximum intensity. Use the distance between two consecutive nodes or two consecutive antinodes to calculate the length of a standing wave. David SantoPietro video https://cdn.kastatic.org/googleusercontent/ODAd7GUM-ZSKVKBS0JqlhLPQ1yQowBaIAU5AyxdZuUEzyKDXlybDAeFtsNQI4Cq5EMVWD0uPhIKpos-pkBxgUbiV Standing waves on strings A standing wave occurs when two waves of the same frequency and amplitude are moving in opposite directions and interfere with each other. It has certain points (called nodes) where the amplitude is always zero, and other points (called antinodes) where the amplitude fluctuates with maximum intensity. Use the distance between two consecutive nodes or two consecutive antinodes to calculate the length of a standing wave. https://cdn.kastatic.org/ka-youtube-converted/gT0IqL1dyyk.mp4/gT0IqL1dyyk.mp4 805 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-behaviors/e/standing-waves-ap-physics-1 2026-04-08T00:16:02.937952483Z Wavelength of standing waves Practice finding the wavelength of a standing wave from a standing wave pattern. Sean exercise https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:wave-behaviors/e/standing-waves-part-2-ap1 2026-03-25T20:00:51.494577527Z Calculating frequency for harmonics of a standing wave Practice calculating the oscillation frequency for different harmonics of a standing wave.  April Russell exercise https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/sound-topic/v/production-of-sound 2023-09-10T17:11:17.624018169Z Production of sound Sound is vibrating air. But how does the air start vibrating? Explore the intriguing science of sound waves and how they travel. Learn how speakers use oscillation to create sound, and discover why sound waves can transport energy without moving the medium itself. Uncover the mystery behind the difference in our voices in person and on recordings. David SantoPietro video https://cdn.kastatic.org/googleusercontent/2pU7GrgIlY3-xI19NU94rl-9GUvs7ZUNRg1RlHiQ4CTZIwCFyXzwHO6WkTz7PbKhaw90s3zRF-VJ32Enk_JepbUH Production of sound Sound is vibrating air. But how does the air start vibrating? Explore the intriguing science of sound waves and how they travel. Learn how speakers use oscillation to create sound, and discover why sound waves can transport energy without moving the medium itself. Uncover the mystery behind the difference in our voices in person and on recordings. https://cdn.kastatic.org/ka-youtube-converted/nGKffdaI4Pg.mp4/nGKffdaI4Pg.mp4 226 Waves https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/sound-topic/v/relative-speed-of-sound-in-solids-liquids-and-gases 2021-03-21T11:26:13Z Relative speed of sound in solids, liquids, and gases Sounds travels at different speeds in different media David SantoPietro video https://cdn.kastatic.org/googleusercontent/vpVRvluy5FRX7ebGyGIAM5fvEFFKsrDcCSn7XAv8pcSnZ1xwl3g-7Jhqijj-E-HV2GzdGojuyrzTHDjrBfkBohg22g Relative speed of sound in solids, liquids, and gases Sounds travels at different speeds in different media https://cdn.kastatic.org/ka-youtube-converted/yF4cvbAYjwI.mp4/yF4cvbAYjwI.mp4 199 Waves https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/standing-waves/v/standing-waves-in-tubes-part-1 2023-09-10T17:11:17.624018169Z Standing waves in open tubes Find out  how ​standing waves and resonance cause a flute makes such specific notes. Discover why blowing over a soda bottle creates a tone, how air molecules oscillate in an open-ended tube, and the mathematical representation of these phenomena. David SantoPietro video https://cdn.kastatic.org/googleusercontent/LaohwgD6FlWiZb_nDxOmbixpGjpmCf7QKZNvcDDM6TQWV88W_FRJMfA5psWVK6806pnsbq_Llbjay-cJq8n43mo Standing waves in open tubes Find out  how ​standing waves and resonance cause a flute makes such specific notes. Discover why blowing over a soda bottle creates a tone, how air molecules oscillate in an open-ended tube, and the mathematical representation of these phenomena. https://cdn.kastatic.org/ka-youtube-converted/BhQUW9s-R8M.mp4/BhQUW9s-R8M.mp4 859 Waves https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/standing-waves/v/standing-waves-in-tubes-part-2 2023-09-10T17:11:17.624018169Z Standing waves in closed tubes Explore the intriguing world of sound waves in open and closed tubes! This lesson breaks down how the length of a tube influences the wavelength and frequency of sound, revealing why you hear different notes as you sip your soda. Discover the unique patterns of harmonics in open-closed tubes, and how they differ from open-open tubes. David SantoPietro video https://cdn.kastatic.org/googleusercontent/fUbmuOh9Jdxon5BSyJHhnD6X8brwsk8wpDqv3HsYP8fnTXS6daNG88xuSrAo1poUDCy93smqUTXpB7D0sdipKvk Standing waves in closed tubes Explore the intriguing world of sound waves in open and closed tubes! This lesson breaks down how the length of a tube influences the wavelength and frequency of sound, revealing why you hear different notes as you sip your soda. Discover the unique patterns of harmonics in open-closed tubes, and how they differ from open-open tubes. https://cdn.kastatic.org/ka-youtube-converted/1S4DtuMY88I.mp4/1S4DtuMY88I.mp4 597 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:sound/e/intro-to-sound-ap1 2026-03-24T23:41:07.080866137Z Wavelength and frequency for sound waves in tubes Practicing calculating the wavelength and frequency of sound waves created in open and closed tubes. April Russell exercise https://www.khanacademy.org/science/in-in-class11th-physics/in-in-11th-physics-waves/in-in-11th-physics-sound-topic/e/pressure-and-displacement-of-standing-waves-in-tubes-ap-physics-1 2026-04-07T23:17:37.123726494Z Pressure and displacement of sound waves in tubes Practice identifying nodes and antinodes for pressure and displacement from a standing wave diagram.  Sean exercise https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/standing-waves/v/beat-frequency 2022-11-16T04:22:43.7414897Z Beat frequency Beat frequency occurs when two waves with different frequencies overlap, causing a cycle of alternating constructive and destructive interference between waves. Learn how this results in a fluctuation in sound loudness, and how the beat frequency can be calculated by finding the difference between the two original frequencies. David SantoPietro video https://cdn.kastatic.org/googleusercontent/DinMTrBRLi0yKtdu3UGrznoI9CRroVwUX8vRz9z2T_IpFKLJEKb5XQIFhmJQ8QX-u-eCMc_r1n1soy_h6jRvxuqx Beat frequency Beat frequency occurs when two waves with different frequencies overlap, causing a cycle of alternating constructive and destructive interference between waves. Learn how this results in a fluctuation in sound loudness, and how the beat frequency can be calculated by finding the difference between the two original frequencies. https://cdn.kastatic.org/ka-youtube-converted/Ca91iOVGd9A.mp4/Ca91iOVGd9A.mp4 708 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:sound/e/beats-ap-physics-1 2026-04-08T00:54:09.631945657Z Analyzing the interference of sound waves and beats Practice analyzing patterns formed when two sound waves interfere.  Sean exercise https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/standing-waves/v/derivation-of-beat-frequency-formula 2021-02-07T17:14:01Z Derivation of beat frequency formula In this video David derives the formula for beat frequency. David SantoPietro video https://cdn.kastatic.org/googleusercontent/uqjBcMhbHxl84Y_eStxnr_7p-7_C97Mwyett3FCUGauV2L7niVZ6oW_EAWgYaLPtzyAv7zAu1RHUpwJogSCT0cUI Derivation of beat frequency formula In this video David derives the formula for beat frequency. https://cdn.kastatic.org/ka-youtube-converted/pI6iJg_W1ug.mp4/pI6iJg_W1ug.mp4 595 Waves https://www.khanacademy.org/science/in-in-class11th-physics/in-in-11th-physics-waves/in-in-doppler-effect/v/doppler-effect-formula-for-observed-frequency 2022-11-16T04:22:43.7414897Z Doppler effect formula for observed frequency The Doppler effect is the change in frequency of a wave as the source moves relative to an observer, and explains why the pitch of a sound sometimes changes as it moves closer or further to or from an observer. Learn how to derive the formula for perceived frequency of a sound using an equation that accounts for a sound and observer’s velocities relative to one another. Sal Khan video https://cdn.kastatic.org/googleusercontent/_usdS17w8l-zyjBt53Cj0CU-vMjLSt8BEsk87Mc0znS1Me8VwCeynIax3PlsPEfbhLktln55Phf_pmdtbEuECFJP Doppler effect formula for observed frequency The Doppler effect is the change in frequency of a wave as the source moves relative to an observer, and explains why the pitch of a sound sometimes changes as it moves closer or further to or from an observer. Learn how to derive the formula for perceived frequency of a sound using an equation that accounts for a sound and observer’s velocities relative to one another. https://cdn.kastatic.org/ka-youtube-converted/kGrk6V8tWDY.mp4/kGrk6V8tWDY.mp4 613 Waves https://www.khanacademy.org/science/in-in-class11th-physics/in-in-11th-physics-waves/in-in-doppler-effect/v/doppler-effect-formula-when-source-is-moving-away 2023-09-10T17:11:17.624018169Z Doppler effect formula when source is moving away Continue your exploration of the Doppler effect by looking at the case where the source is moving away from the listener. Understand the formulas for observed frequency when the source is moving towards or away from the observer. Apply these concepts to real-world scenarios like the changing pitch of a moving train's horn. Sal Khan video https://cdn.kastatic.org/googleusercontent/IFKQk0CdMx_wFOC-D3ov-m-VPPhkDtsaMIgRQu4mke2LgURzRWL5m7bLpJwdxUyIFRU7LVW0sJvXkomDre3jufo Doppler effect formula when source is moving away Continue your exploration of the Doppler effect by looking at the case where the source is moving away from the listener. Understand the formulas for observed frequency when the source is moving towards or away from the observer. Apply these concepts to real-world scenarios like the changing pitch of a moving train's horn. https://cdn.kastatic.org/ka-youtube-converted/KkJ0wL9f2VY.mp4/KkJ0wL9f2VY.mp4 558 Waves https://www.khanacademy.org/science/physics/mechanical-waves-and-sound/doppler-effect/v/doppler-effect-for-a-moving-observer 2023-09-10T17:11:17.624018169Z Doppler effect for a moving observer What happens when just the observer is moving? Explore the Doppler effect in sound waves as we examine how the frequency changes when an observer moves towards or away from a sound source. Understand the formulas used to calculate observed frequency, and how speed influences the pitch of the sound. David SantoPietro video https://cdn.kastatic.org/googleusercontent/keP83jiV3hOW5p5wXA-Q8Mxl4u1JnqMdk4_KjzgnM0pnHot1d82hrcly2i0TUuajF_x9Wzka5cYbpfkQg3z2brDDzA Doppler effect for a moving observer What happens when just the observer is moving? Explore the Doppler effect in sound waves as we examine how the frequency changes when an observer moves towards or away from a sound source. Understand the formulas used to calculate observed frequency, and how speed influences the pitch of the sound. https://cdn.kastatic.org/ka-youtube-converted/2TTu0TvB6N0.mp4/2TTu0TvB6N0.mp4 316 Waves https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:waves-sound-and-physical-optics/x0e2f5a2c:sound/e/doppler-effect-ap1 2026-04-08T00:16:02.937952483Z Doppler effect Predict how different observers hear different frequencies from a word problem or wavefront diagram. April Russell exercise