If a soap bubble becomes dark when the path length difference is less than one fourth the wavelength, what is the thickest the soap film can be and appear dark at all visible wavelengths? give your answer in nanometers.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

i think the answer is a and b

i wish you luck

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2