PHYSICS PRESENTATION FOR TOK PARTICLES AND WAVES Making sense of the world Describing Predicting How do we measure the differences we see? x y z Two identical blocks in different places Two non simultaneous identical events at the same place Length Time

Movement Ball moves in space and time This is a particle S=vt Mathematical model of the motion Represented by a graph t v This is not the ball moving it is graph representing it, a model. There is no equation hanging in space We can use the model to make predictions We can test the model by experiment

What happens when two balls collide? ? NEWTONS LAWS OF MOTION Used to solve problems, if the law says so then it must be right. If the dog pulls the man with force F how hard does the man pull the dog? The answer is -F The answer needs no further justification

The laws of physics can not be broken No need for physics police or judges The apple falls because of gravity, gravity is what makes the apple fall Newtons UNIVERSAL law of gravity Slightly arrogant!

Invisible Particles Idea began in ancient Greece - Atoms Can be used to explain difference between solid liquid and gas A blue line coming out of a hot wire passing into an electric field falls in the same way as a ball Maybe the blue line is made of particles

Light Light reflects like a ball bouncing off a wall But two light sources can cancel each other out, balls don’t do that See here, the light reflecting off the front and back of the bubble has made a dark patch. Water waves do this. Maybe light is a wave.

What is a wave? Water wave Mexican wave Ripple tank Electrons cancel out too! Electron beam No electrons Electrons also have wave properties Light bounces off an electron This is a particle property, so light must be a particle too.

This is how we understand it to be: The probability of interaction between two regions of space (particle) is governed by a probability distribution (wave). So we use the particle when there is an interaction and the wave to tell us when and where the interaction will take place. Electrons waiting for an interaction Wave equation predicts no interaction here Electron waiting to pass through slit But very likely here Consider this

Questions Can anything be two things at once? Do electrons really exist or have they just been invented by man? Can we write universal laws from our position on the earth? Does any of this really matter