I will give you brainiest

Radioactivity is a part of our earth - it has existed all along. Naturally occurring radioactive materials are present in its crust, the floors and walls of our homes, schools, or offices and in the food we eat and drink. There are radioactive gases in the air we breathe. Our own bodies - muscles, bones, and tissue - contain naturally occurring radioactive elements.

answer: 31, 5556. 952 seconds

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray