Term+4+Light

__ How we see colours __

media type="youtube" key="gtgBHsSzCPE" height="315" width="560"

media type="youtube" key="Hbxy1W9O_Wk" height="315" width="420"

Video on Refraction media type="youtube" key="fD1544bM_c4" height="315" width="420"

Light, Shadow and Time media type="youtube" key="yN61ndEMe4E" height="315" width="420"

The speed of light in a vacuum is defined to be exactly 299,792,458 [|m/s] (approximately 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation are believed to move at exactly this same speed in vacuum. Different [|physicists] have attempted to measure the speed of light throughout history. [|Galileo] attempted to measure the speed of light in the seventeenth century. An early experiment to measure the speed of light was conducted by [|Ole Rømer], a Danish physicist, in 1676. Using a [|telescope], Rømer observed the motions of [|Jupiter] and one of its [|moons] , [|Io]. Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about 22 minutes to traverse the diameter of [|Earth] 's orbit. [|[4]] However, its size was not known at that time. If Rømer had known the diameter of the Earth's orbit, he would have calculated a speed of 227,000,000 m/s. ~Yoke Ting~ :)