What Shows the Wave-Particle Duality of Light in the Compton Effect Experiment?

[Mr.somebody]

Homework Statement

What quantity measured in the Compton effect experiment show the wave-particle duality of light?

Homework Equations

The Attempt at a Solution

the question is out of 2 marks and all I can think about is momentum is there anything I am missing or am i completely wrong?

 

[Mr.somebody]

I think it might be wavelength and frequency can anyone let me know if I am correct