"Frequency" just means "often-ness" ... how often something happens.
It's always expressed as
<em>(number of happenings) / (some period of time) .</em>
The answer is ultra violet radiation. From the air
Work = force × distance
= 35 N × 200 m
= 7000 J
Because way back, when there were some kinds of plants that made
their own food, and other kinds of plants that depended on dinosaurs or
people to bring them food, guess which ones starved and became extinct,
and which ones lived and are still among us today.
