What is the principle of perception that supports the idea that your brain expects that the puff of white between the fingers is a cloud; that is much farther away than the hand?

Which of the following activities would conserve the most energy? installing a dimmer switch on a light using a blender instead of a food processor hanging clothes to dry on a clothesline instead of ironing them opening a window instead of turning on the air conditioning setting your computer's screen saver to turn on after less time has elapsed