The atmospheric pressure is due to the
(a) sky above our head (b) air mass surrounding the earth
(c) gravitational force of sun and other planets. (d) mass of the earth

Ascientist notices that an oil slick floating on water when viewed from above has many different colors reflecting off the surface, making it look rainbow-like (an effect known as iridescence). she aims a spectrometer at a particular spot and measures the wavelength to be 750 nm (in air). the index of refraction of water is 1.3