Why is anthracite a better fuel than lignite?

Diffraction is when light is bent around obstructions. which of the these observation about clouds would indicate diffraction? a) after rain storms, you can sometimes see rainbows. b) clouds are white or gray and cannot be seen through. c) on a cloudy day, the temperature tends to be cooler than a sunny day. d) the edges of dark clouds appear lighter. this

What is the source of continuous heat and energy that we receive from the sun

Ahelium balloon contains 16.9 l of helium at stp. how many atoms of helium are in the balloon