# To find the speed of light in glass using Snell's Law / To prove the Snell's Law

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Introduction

Name: Jonathan Tam Class: 12A

Phyiscs

Experiment Report – Data Processingand Presentation, Conclusion & Evaluation

Aim: To find the speed of light in glass using Snell’s Law / To prove the Snell’s Law

Data Collection:

Speed of light in air: 299702547 ms-1

(From http://www.what-is-the-speed-of-light.com)

Angle of incidence (± 0.5°) | Angle of reflection (± 0.5°) |

63 | 37 |

54 | 32 |

42 | 26 |

34 | 22 |

26 | 16 |

25 | 15 |

11 | 8 |

Data Processing and Presentation:

We can simply plug in the values of , and into the equation

Middle

0.438

0.276

0.423

0.259

0.191

0.139

By rearranging the formula, we have:

So we need the value of then take the avrage of this ratio and multiply it by the speed of light in air.

0.675 |

0.655 |

0.655 |

0.670 |

0.629 |

0.612 |

0.729 |

Average: 0.661

Please be aware that this is a ratio which has no units.

0.661 * 299702547 ms-1 = 198063544ms-1

We have the equation , which follows the pattern y = mx. We can plot a graph in order

Conclusion

There are few limitations in this experiment.

Apparatus / Variable | Limitations / Discussions | Improvements |

Protractor | High uncertainty / Not precise enough | Make the angle larger to decrease percentage error |

Light ray | Light ray is diffracted and is hard to determine the angle of incidence and refraction | Use a lens to focus the light rays in order to narrow it |

Material of refraction | Uncertain whether it is purely glass or partly glass (might be mixed with other materials eg plastc) | Check and see if the container cleaerly says “glass block” or “plastic block” |

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

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