A level Physics: Wave Particle Duality

• Light is part of the electromagnetic spectrum
• The theory of the electromagnetic waves predicted the existence of waves beyond visible light (before we knew about x-rays and so on)
• The discovery of x rays and radio waves confirmed their existence (and their predictions)
• Many scientists in the late 19th Century thought that all aspects of physics could be explained through Newton's laws of motion. 

Interference and Diffraction show light as a wave

• Light produces interference and diffraction patterns - these are alternating bands of dark and light
• Can only be explained using waves interfering constructively or interfering destructively

Constructive Interference - when two waves overlap in phase

Destructive interference - when two waves are out of phase

Although - Particles DON'T show wave-like properties all the time

Diffraction only happens if a particle interacts with an object about the same size as the de Broglie wavelength

de Broglie came up with the wave-particle duality theory

shorter wavelength = less diffraction effects (this fact is used in electron microscopes)
Diffraction effects blur detail on an image 

(specifically for AQA A-level physics specification A)