The Tools Used to Measure Density
Scale. Mass is one of the most easily obtained measurements. ...
Graduated Cylinder. The most accurate way to determine an object's volume, especially in the case of an irregularly shaped object, is to immerse it in water and measure the amount of water it displaces. ...
Calculating Density. ...
Hydrometer. ...
The Value of Density.
Answer:

Explanation:
v = Velocity of the breeze = 4 m/s
w = Width of the valley = 5000 m
h = Height of the valley = 1000 m
Volumetric flow rate is given by

= Mass flow rate of pollutant = 25 g/s = 
Concentration is given by

The steady state concentration of pollutants in the valley, is
.
I think the correct answer would be one half the wavelength. Waves would "feel bottom" when the water is at the depth of 0.5 of the wavelength. "Feel bottom" is a term used to describe that the depth of water affects the wave properties. Hope this answers the question.
Gamma rays, X-rays, most ultraviolet rays, and some infrared are absorbed by the atmosphere but do not reach the Earth's surface