How much pressure is required to compress 1L volume of air at 1atm pressure to 0.5L

This element exists in adundance in the sun. explain how you would go about capturing sunlight. would this captured sunlight contain any of the element?

Which process does not require the presence of a physical substance in order to transfer heat? air in the atmosphere is heated by the ground. this warm air then rises, and cooler air falls. this is an example of what type of process? how is conduction different from radiation?

Light waves are as they pass through the