How do we use the speed of light in the real world?
There are a number of uses of speed of light in our daily life. The SI unit of distance measurement, meter, is defined by using the speed of light. A meter is the distance travelled by light in 1/c seconds, where C is the speed of light. We use distance measurement several times a day (like the distance of a vehicle from us, during driving, etc.). Another application of speed of light is in lasers, which travel at the same speed as light and are used in our daily life. Another application of speed of light is during driving, especially at night. The light of oncoming vehicles gives us an idea of their distance from us and is also used to figure out turns in the road.
Hope this helps.