damping | Putting Energy Into Vibrations |

de Broglie wavelength | Electrons as Waves |

death of the universe | The heat death of the universe |

deceleration | Positive and Negative Acceleration |

definition | The Gravitational Field |

| The Electric Field |

derivative | Applications of Calculus |

dialogue | Scaling of Area and Volume |

diffraction | Double-Slit Diffraction |

| Summary - Wave Optics |

diffuse reflection | Interaction of Light with Matter |

diffusion | Ions moving across a cell membrane |

diopter | Diopters |

dipole | Dipoles |

dipole moment | Dipole moment of a molecule of NaCl gas |

discussion questions | Discussion Questions - Electric Fields |

| Discussion - Refraction and Images |

| Discussion - Angular Momentum |

distribution | Applications of Calculus |

Doppler effect | The Doppler Effect |

Doppler shift | The Doppler Effect |

| Summary - Wave Motion |

| Doppler-shifted sound from a race car |

| Doppler shift of the light emitted by a race car |

| The Big Bang |

dot product | The Dot Product |

double-slit diffraction | Double-Slit Diffraction |

| Summary - Wave Optics |

download | Download and Release History |