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For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above the ground and tops up to 15 km (9.3 mi) in height. The place on Earth where lightning occurs most often is over Lake Maracaibo , wherein the Catatumbo lightning phenomenon produces 250 bolts of lightning a day. [ 82 ]
Comfortable bicycling speed. 10 1: ... 320 km/h or 200 mph is a parameter sometimes used in ... Typical speed of the stepped leader of lightning (cf. return stroke ...
The most noticeable aspect of lightning and thunder is that the lightning is seen before the thunder is heard. This is a consequence of the speed of light being much greater than the speed of sound. The speed of sound in dry air is approximately 343 m/s (1,130 ft/s) or 1,236 km/h (768 mph) at 20 °C (68 °F; 293 K). [19]
[10] [11] Positive clear-air strikes can occur in highly sheared environments where the upper positive charge region becomes horizontally displaced from the precipitation area. [12] Cloud-to-air lightning is a lightning flash in which one end of a bidirectional leader exits the cloud, but does not result in a ground flash. Such flashes can ...
Global map of lightning frequency--strikes/km 2 /yr. The high lightning areas are on land located in the tropics. Areas with almost no lightning are the Arctic and Antarctic, closely followed by the oceans which have only 0.1 to 1 strikes/km 2 /yr. The map on the right shows that lightning is not distributed evenly around the planet. [5]
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But light travels 300,000 km/sec, almost a million times the speed of sound. ... that is, if the lightning is closer than 8 km or 5 miles.