Daniel is standing a certain distance from a wall and claps. He hears the echo 4s later. How far away is the wall? Remember that the sound has travelled to the wall and come back.
(Take the speed of sound in air to be 330 m/s).

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete

pecialized keyboards

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.