Please help Wave interference occurs when?

Waves bounce off of each other
Waves pass through each other
A wave bounces off a barrier
A wave passes from one medium to another

Blank liquids and gases exert a buoyant force on objects placed in them

If an atom contains 11 protons in its nucleus, predict the element with the atomic number and electronic configuration. will the number of electrons remain the same during the chemical reaction in such an atom? explain.

Ablock having mass m slides down an inclined plane. the force of friction between the block and the inclined plane is f, the block's weight is m g, and the normal force is n. (a) draw a free – body force diagram showing the forces acting on the block. (b) write down all relevant newton’s equations for a given situation.