Question

The light from a laser beam travels at a speed of 300000000 m/s how far it is seen after 20 nano seconds

Answer 1

given that speed of laser light is

$v = 300000000 m/s$

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

time of travel

$t = 20 ns$

$t = 20* 10^{-9} s$

distance traveled by the light

$d = v*t$

$d = 3*10^8 * 20*10^{-9}$

$d = 6 m$

so it will travel a total distance d = 8 m in given time

Answer 2

Given that we are working with different units we need to do some conversions.

We do the conversions as follows:

1 nanosecond = 1 × 10⁻⁹ seconds

20  nanoseconds will therefore be given as follows:

= 2. 0 × 10⁻⁸ Seconds  

We use indices to make our work simpler and easier.

Speed of light = 3.0 × 10⁸ m/s

The formula for finding distance is given as :

Distance = Speed × time

We do the substitution as follows to get:

Distance = 3 × 2 × 10⁸ × 10⁻⁸

By law of indices we add the powers to get:

(-8 + 8) = 0 hence:

= 6 × 10⁰

= 6 meters