# How is the Snell-Descartes law written?

**Sommaire de notre article**

- How is the Snell-Descartes law written?
- What is the unit of refractive index?
- How to calculate the refractive index of a medium?
- Why does the refractive index have no units?
- How to measure refractive index?
- How to calculate a refractive index?
- Is the refractive index less than?
- Who created the law of refraction?
- What is the refractive index of a vacuum?

### How is the Snell-Descartes law written?

The **Snell’s law**‘**written** simply: ni x sin(i)= nr x sin(r) where i and r are respectively the angles of incidence and refraction (in radians).

### What is the unit of refractive index?

L’**refractive index** has no**unity** measurement: it represents a factor indicating **the** slowing down of light in **the** medium relative to the vacuum.

### How to calculate the refractive index of a medium?

L’**refractive index of a medium** is equal to the ratio of the speed of propagation of light in vacuum to that in this **environment**.

### Why does the refractive index have no units?

L’**refractive index** n characterizes a transparent medium where n is a number without **unity**, greater than or equal to 1. different medium, it must be different, in this case it is noted v. therefore n ≥ 1 because c is a speed limit in the universe and that we cannot therefore **not** to go past.

### How to measure refractive index?

The **measure** of the’**refractive index** is carried out using a precision electronic refractometer, the temperature of which is regulated by a thermostated circulation bath.

### How to calculate a refractive index?

The calculation of a refractive index can be done using two different methods. That is to say by calculating the ratio of the speed of light in vacuum compared to that in the medium. This method implies that the celerity of light in the medium is known or can be found from the data of the situation studied.

### Is the refractive index less than?

On the one hand, because the speed of light in vacuum is an upper limit to the speed of light, one could deduce that the refractive index cannot be less than , which is false.

### Who created the law of refraction?

René Descartes published this law of refraction in “La Dioptrique” in 1637. Birefringence in a crystal of calcite (or Iceland spar): refraction splits the text. Descartes had demonstrated the relationship based on false assumptions about the speed of light.

### What is the refractive index of a vacuum?

c vacuum has the value 3.00.10 8 m/s or 3.00.10 5 km/s There is no material medium where light propagates faster than in vacuum therefore an index of refraction is always a higher number or equal to 1.