The right answer to this question is A. a crest that is toppling over. When a surfer rides an ocean wave on her surfboard, she is actually riding on a crest. The crest is the point on a wave with the maximum value or upward displacement within a cycle.
Answer:
Explanation:
Chemical properties only manifest when a chemical reaction occurs. Being reactive, flammable and explosive are chemical properties, because they involve chemical reactions: the substances are changed; the chemical bonds of some substances, called reactants, are broken, and the chemical bonds are created, forming other substances, called products.
Solubility is a<em> physical property</em> because during dissolution no new substances are formed. You can prove it when the solvent evaporates leaving behind the same original substance.
The the observation that the substance is <em>soluble</em> is describing a <em>physical property.</em>
<span>a change in allele frequencies in a population over time also known as evolution</span>
Explanation:
Here,
object distance(u)=20cm
image distance(v)=80cm-20cm=60cm
focal length(f)=?
we know ,
(1/f)=(1/v)+(1/u)
1/f = 1/60 + 1/20
1/f = (1+3)/60
60 =4f
f=15cm
