Does every scientific method begin with and observation?

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.

Determine the maximum r-value of the polar equation r =3+3 cos 0

Which form of cell division creates the sperm and egg, resulting in half of the chromosomes as the other cells?