Oscillations and waves
Introduction to sound waves
Observe sound in air as a longitudinal wave: the surface shows pressure variation with position while gas layers oscillate along the propagation direction. Vary wavelength and frequency to verify .
⚠ When listening to real sound from speakers or tuning forks, keep the volume moderate and avoid ears near loud sources — high sound intensity damages hearing.
Equipment
- 3D canvas showing the pressure surface of a sound wave, rotated by dragging or arrow keys
- Sliders «Biên độ áp suất», «Bước sóng λ» and «Tần số f»
- Readout line showing «Vận tốc âm v = λf»
- «Tạm dừng» / «Chạy tiếp» button to freeze the wave pattern
Procedure
Read the speed of sound from wavelength and frequency
Set «Bước sóng λ» and «Tần số f» to any values and look at the readout line: «Vận tốc âm v = … m/s». Check that the displayed number equals the product of the two sliders, i.e. . Change λ, then f, and re-read v each time.
Distinguish the roles of amplitude and frequency
Increase «Biên độ áp suất» and watch the surface grow taller — a louder sound — while the readout v stays fixed. Then change only «Tần số f»: the crests sweep faster, a higher pitch, and v follows the model's . Conclude that frequency sets pitch while pressure amplitude sets loudness.
Rotate the view and identify a longitudinal wave
Press «Tạm dừng» to freeze the picture, then drag the canvas (or focus it and use the arrow keys) to view the surface from several sides. Recognise compression–rarefaction travelling along the propagation direction — the signature of sound in air — then press «Chạy tiếp» and predict the new v before changing λ or f.