---
title: 'Wave or corpuscules? or both ...'
media_order: 'corpuscule-trajectory-tennis-ball.jpg,refraction-cuillere.jpg,sky-light-rays-827.jpg,wave-corpuscular-nature-of-light-experiment1.gif,waves-interferences-surface-water-827-496.jpg,reflexion-statuette.jpg'
---
### How do we understand our physical world ?
* We interpret the world with two intuitive concepts that are in our mind mutually exclusive : the concept of corpuscule and the concept of wave
##### Localized corpuscules with trajectories
In our mind, a **corpuscule** is *localized in space*, and **At each instant** can be characterized by :
* a *position in space*
* a *speed*
* an *acceleration*
It carries :
* *matter*
* *energy*
* *momentum*
Between two instants, its movement describes a *trajectory* : continuous set of positions followed by the corpuscule between these two instants.
The **behavior of a corpuscule** *at human scale*, and **their interactions with each other**, is well described and predicted by *classical mechanics*.
* **classical mechanics** = **Newton's mechanics** = **point mechanics**
##### Waves that interfer to each other
In our mind, a **wave** is *not localized in space*, and **in the whole time** can be characterized by :
* a *frequency*
* a *velocity*
* frequency + velocity $\Longrightarrow$ a *wavelength*
* an *amplitude*
* a *polarization* (depending of wave type)
A wave
* *does not carry matter*
* *carries energy*
**Several waves** interfer with each other, giving rise to *interferences*
A wave **passing through a small aperture** (of size of the order or small than wavelength) is *diffracted*
### How light behaves ?
A modern Youngs'type experiment :
behavior of light passing through two slits and
The light emerging from a double slit, whose the width (of each slot) and the spacing (between the two slots) are sufficiently small,
### What optical phenomena do we observe in everyday life ?
* The **light** describes in *straight lines in air*.
$\Longrightarrow$ concept of *light ray*
##### Refraction phenomenon
* The light seems to *change direction from water to air*.
* can be d
##### Reflection phenomenon
