Lines of a particular element appear at the same wavelength in both emission and absorption line spectra. true or false

Each atom emits or absors electromagnetic radiation, but only in some frequencies that are characteristic of its chemical element.  

Now, if we supply energy in the form of heat (thermal energy) to a certain element in its gas phase, this will be stimulated and its atoms will emit radiation in certain frequencies of the visible spectrum, which constitute its emission spectrum.  

If the same element, also in gaseous state, receives electromagnetic radiation, it absorbs in certain frequencies of the visible spectrum, precisely the same ones in which it emits when it is stimulated by heat. This will be its absorption spectrum.  

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.