Why do the terrestrial planets lack hydrogen and helium in their atmospheres? a. hydrogen and helium were blown away by solar wind. b. hydrogen and helium were converted to other compounds as the planets formed. c. hydrogen and helium can't be retained because the planet masses are too small. d. hydrogen and helium are present in rings around the terrestrial planets.

Aknife blade is a(n) a. lever b. screw c. wedge d. inclined plane

True or false when elements combine to form a mixture, the resulting chemical properties may be very different from those of the elements that make it.

Alinearly polarized electromagnetic wave has an average intensity of 196 w/m^2. this wave is directed towards two ideal polarizers (in real polarizers, transmission is also effected by reflection and absorption). polarizer a is oriented with its transmission axis at an angle of θ_1=20.8∘ with the incident electric field. polarizer b has its axis at an angle of θ_2=63.0∘ with the incident electric field. what is the average intensity of the wave after it passes through polarizer a? what is the average intensity of the wave after it passes through polarizer b? suppose that the two polarizers a and b are interchanged. what would the average intensity be after passing through both polarizers?