1 What do the characteristics of electromagnetic radiation include?
A. characteristics of particles only
B. characteristics of waves only
C. characteristics of both waves and particles
D. characteristics of neither waves nor particles

2 Which equation correctly relates the energy of electromagnetic radiation to its frequency?
A. E=h/v
B. E=hv
C. E=v
D. E=h

3 What causes electrons in atoms to emit energy after absorbing it?
A. being ripped off their atoms
B. returning to their ground energy states
C. losing mass
D. becoming electromagnetic radiation

4 What observation led scientists to postulate the existence of photons?(1 point)
A. electrons in atoms emitting energy only in certain amounts
B. seeing photons through powerful microscopes
C. discovering that electrons can have varying amounts of energy
D. electrons in atoms emitting energy across the electromagnetic spectrum