How Sunny does it have to be outside for a magnfiyglass to start a fire?

Question

How Sunny does it have to be outside for a magnfiyglass to start a fire?

Answer 1

That depends on the size of the magnifying glass.  A large glass (4 to 5 inches in diameter) collects more light than a small one (1 to 2 inches in diameter) and will start a fire easier.

Answer 2

Sunny enough for a maginfying glass to start a fire

Answer 3

As long as you have visible light hitting the lens it will coalesce the rays into one small area enough to heat up whatever is underneath it ......but you need to consider the flashpoint of whatever material you are trying to ignite (I think I heard that the flashpoint of paper was 451 degrees F...no clue on ants tho :P) and also the UV index for that day - ultra violet and violet light have higher frequencies than red or yellow light, and higher frequencies heat molecules up faster