Why do cats like boxes?

They're the YouTube classics which rack up potentially millions of views, cats sliding around the living room in boxes - but why do they have this obsession?
In the wild, cats hide in bushes or burrows during the day to escape their many predators. Scientists believe that it's this trait which lingers in domestic cats. Studies have indicated that cats in animal shelters feel far more comfortable if they had a box to hide in. Even when cats aren't stressed it still can make them feel more comfortable and secure.

AS Physics - Electron Diffraction

(for AQA AS Physics)

• Electron diffraction shows the wave nature of electrons (how electrons can behave like waves)
• Diffraction patterns are observed when accelerated electrons in a vacuum tube interact with the spaces in a graphite crystal - this confirms electrons show wavelike properties
• According to the wave theory - the spread of the lines in the diffraction pattern increases if the wavelength of the wave is greater
• In experiments: a smaller accelerating voltage (the electrons are slower which gives widely spaced rings
• Increase in the electron speed - the diffraction pattern circles squash together towards the middle. (fits with the de Broglie equation  - if velocity is higher the wavelength is shorter and the spread of the lines smaller)

Wavelength for electrons accelerated in a vacuum tube is about the same size as electromagnetic waves in the X-ray part of the spectrum

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)