Physical science. Yes.
Stays the same
Could increase, decrease, or stay the same
All of the above could form diffraction patterns
Electrons in atoms
Planets in orbit around the sun
The space shuttle in orbit around Earth
Billiard balls on a pool table
Brownian motion of dust particles in the air
Quantum mechanics doesn't apply to big objects
They are larger than the wavelength of light
Their wavelengths are too short
They can't fit through small slits
They don't have wave properties
Here's an interesting quiz for you.