80 i need a step by step simple experiment to show that light travels in straight lines until at a point were it enters a new medium.

Does anyone know a lot about how to: - calculate mass of magnesium metal - calculate the actual yield of magnesium oxide - calculate the theoretical yield of mgo - calculate the percent yield of mgo - determine the percent yield of mgo - determine the average percent yield of mgo i had to do an online lab and its asking these questions but i have no idea where to start or how to be able to find these things. i can post the chart of the data from the lab or if you can tell me exactly how i can find each.

Why are pipes bursting in the in extremely cold weather?

How does the principle of electromagnetism explain the interaction between earth’s magnetic field and the solar wind?