Question

Light travels at a speed of about 3.0 108 m/s. (a) how many miles does a pulse of light travel in a time interval of 0.1 s, which is about the blink of an eye? Δx = 3 mi (b) compare this distance to the diameter of earth. (use 6.38 106 m for the radius of the earth.) δx de =

Answer 1

Speed of light is given as

$c = 3 * 10^8 m/s$

time interval is given as

$\Delta t = 0.1 s$

so the distance covered by the light is given as

$d = v * \Delta t$

$d = 3 * 10^8 * 0.1 = 3 * 10^7 meter$

now as we know that

$1 mile = 1609 meter$

so the distance moved by light is

$d = \frac{3 * 10^7}{1609} = 18645.12 miles$

now for the comparision of this distance with diameter of earth

as we know that radius of earth is

$R = 6.38 * 10^6 m$

so the diameter of earth will be

$d = 2R = 12.76 * 10^6 m$

now the ratio of diameter with the distance that light move will be

$\frac{distance}{diameter} = \frac{3 * 10^7}{12.76 * 10^6}$

$\frac{distance}{diameter} = 2.35$

so it is 2.35 times more than the diameter of earth