Does doubling the time of an investment double the amount of interest earned? explain with words and an example

Sure it does. 
For example U have let out $10,000 at the rate of 10% p.a 
Then ur interest for the One year will b = 10,000*10/100*1 
= $1000 p.a 

If you double the time to Two years = 10,000*10/100*2 
then your interest will b 
=$2000 p.a 
So its double.