On a warm summer day (33 ∘C) , it takes 4.70s for an echo to return from a cliff across a lake. On a winter day, it takes 5.10s. The speed of sound in air is v≈(331+0.60T) m/s, where T is the temperature in ∘C. What is the temperature on the winter day?

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