The propagation speed of light in a transparent substance is about 25 times of that in a vacuum, and the propagation distance of light in 60 seconds is about 20___ Rice

The propagation speed of light in a transparent substance is about 25 times of that in a vacuum, and the propagation distance of light in 60 seconds is about 20___ Rice


∵ the propagation velocity of light in vacuum is v = 3 × 108m / s, then the propagation velocity of light in a transparent material is v '= 25V = 25 × 3 × 108m / S = 1.2 × 108m / s, and the propagation distance of light in the transparent material for 60 seconds is s = v't = 1.2 × 108m / s × 60s = 7.2 × 109m