### August 31, 2004

### 2004.08.31 Answer to the Poll...

**Question:** *Speed of light in free space is c=3x10^8 m/s. Find the time (in secs) for the light to travel 1 m.*

**Answer:** 3.3x10^-9 secs

**7 answered** that question correct.

Here's the proof...

Since speed is a measure of distance over a length of time, the basic equation can be written like this:

Since we're looking for the length of time to traverse 1 meter, the equation can be re-written to solve for time:

We plug in the values:

**1 meter**/

**3.3x10^8 (meters / second)**

Now, we multiple 1 second to both the numerator and the denominator which will cancel out the seconds that's in the **demoninator** and leaves the unit of measure as (meters * seconds) in the **numerator**. But because meters in both the numerator and the denominator cancel each other out, leaving out **seconds** in the numerator position.

Time = ( 1 / 3.3 x 10^8 ) seconds **OR 3.3 x 10^-9 seconds**

and thank you, for that piece of information that is so useful to me :)...

:/