Calculate the frequency of each wavelength of electromagnetic radiation: 12.24 cm (wavelength of microwave oven)

most of them using statistics and defining how things are being measured

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )