Acid-base indicator changes color based on pH.
drop some in a solution n watch the color changes. different indicators show different colors at different pH. they usually have standard colors for comparison.
Wave "B" is thinner. Is this the whole question?
Answer: 300mm
Explanation:
30cm x (10mm/1cm) x <em>(1mm/1mm)</em> = 300mm
<em>Btw, I'm not sure about the </em><u><em>(1mm/1mm).</em></u>