Knowledge Gallery
Welcome to Gallery of Knowledge
Online Knowledgeable Articles  
Knowledge Gallery Home Knowledge Gallery Home | Knowledge Gallery Glossary Glossary | Contact Us Contact Us
Knowledge Gallery Home > All Categories > Educational Knowledge > Science > what is the speed of light ?
Question Title what is the speed of light ?

The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning "swiftness". It is the speed of all electromagnetic radiation in a vacuum, including visible light, and more generally it is the speed of anything with zero rest mass.

In metric units, c is exactly 299,792,458 metres per second (1,079,252,848.8 km/h) but 3×108 m/s is commonly used in rough estimates. Note that this speed is a definition, not a measurement. Because the fundamental SI unit of length, the metre, has been defined since October 21, 1983 in terms of the speed of light, one metre is the distance lightAAA+ 2015 New Fashion cheap replica watches Piguet replicareplica watches uk Replica WatchesIWC Replica Watchesbreitling replicaPatek Philippe Replicacopy watches REPLICA WATCHES is Very Special In Our Store.
travels in a vacuum in 1/299,792,458 of a second. Thus, any further increase in the precision of the measurement of the speed of light will actually change the length of the metre; the speed of light will remain precisely 299,792,458 m/s. In imperial units, the speed of light is about 186,282.397 miles per second, that is about one foot per nanosecond.
A line showing the speed of light on a scale model of Earth and the Moon
A line showing the speed of light on a scale model of Earth and the Moon
When passing through a transparent or translucent material medium, like glass or air, light will have a slower speed than in a vacuum; the ratio of c to the observed phase velocity is called the refractive index of the medium. In general relativity, a gravitational potential can affect the speed of distant light in a vacuum, but locally light in a vacuum will always pass an observer at a rate of c.
Article Source : Speed of Light
Authored by: Rahul Bhanot This question has been viewed 3610 times so far.
Click Here to View all the questions in Science category.
File Attachments File Attachments
There are no attachment file(s) related to this question.
How helpful was this article to you?
Related Questions Related Questions
  1. What is Physics?
Article Information Additional Information
Article Number: 41
Created: 2007-07-20 9:39 AM
Rating: 3 out of 5
Rate Bar: 3 Stars
Article Options Article Options
Print Question Print this Question
Email Question Email Question to Friend
Export to Adobe PDF Export to PDF File
Export to MS Word Export to MS Word
Bookmark Article Bookmark Bookmark
Reditt Bookmark Reditt Bookmark
Digg Bookmark Digg Bookmark
Subscribe to Article Subscribe to Article
Search Knowledge Gallery Search Knowledge Gallery

Related Articles Related Articles

Related What is Physics?


Powered by PHPKB Knowledge Base Software