Brewsters Law Formula

Brewsters Law Formula

It is mandatory that students bring polarised sunglasses when they go hiking. Consequently, when the weather is sunny, the lake’s reflection is impossible to miss. They are polarised reflections. However, students will note that these reflections are gone when they look at it via their sunglasses. The fact that the sunglasses are polarised explains why it occurs. Only polarised light may pass through them. In addition, polarizers may be found in monitor and TV displays to lessen glare. On the Extramarks website and mobile application, students may learn more about Brewsters Law Formula.

Students can access the Brewsters Law Formula notes and solutions via the Extramarks website and mobile application. The Brewsters Law Formula notes have been designed and curated in a very easy-to-understand and comprehended manner. Experts have made sure to provide detailed and descriptive information throughout the notes explaining the Brewsters Law Formula.


The reflected light is polarised, but not all of it, as students are aware. It produces light that is polarised at a 90° angle to the plane of a reflection when it is in that plane. That will probably reflect more. In reality, the angle at which the light is shone has a significant influence on how polarised the reflection will be. Brewsters Law Formula is thus made available for students to help them in describing how it changes with angle.

The Brewsters Law Formula states that the highest amount of polarisation occurs at an angle of 90 degrees between the reflected and refracted rays. This statue bears Sir David Brewster’s name, a renowned Scottish physicist. In 1811, a proposal was made. Additionally, Brewster’s angle applies to the polarisation angle as well.

The notes and solutions based on the Brewsters Law Formula are downloadable in high quality and students can use them to prepare well for their examinations.

Brewsters Law

According to Brewsters Law Formula, the best way to polarise light is to let it strike the surface of a transparent material so that the refracted light is perpendicular to the reflected light. It establishes a connection between the refractive index and the polarising angle ip. It claims that the refractive index of the medium is mathematically equivalent to the tangent of the polarising angle.

When all of the reflected light is completely polarised at a particular angle of incidence, this angle of incidence value is known as the polarising angle. The transparent material’s refractive index mu determines the polarising angle ip.

The relationship is written as = tan ip.

Over here:

Refers to the clear medium’s refractive index.

The polarising angle of incidence abbreviated ip and equal to the Brewster angle

The rays that transmit and reflect when unpolarised light is incident on a transparent substance at any polarising angle are parallel to one another.

Examples have been cited wherever needed in the notes, and solutions based on the Brewsters Law Formula provided by Extramarks experts. Students can use these notes and solutions based on the Brewsters Law Formula offered by Extramarks for self-study purposes. They can also use it to strengthen and brush up on the basics of the Brewsters Law Formula, thereby improving their results.

Solved Examples

Example 1: If a polariser’s refractive index is 1.9218, I have a question. What will the polarisation and refractive angles be?

Answer – Looking at the above numbers, we will notice that we already know the refractive index of the polariser, which implies μ is 1.9218. In order to obtain the polarisation angle and angle of refraction, we shall apply Brewster’s law:

μ = tan ip

or ip = tan1tan1 (1.9128)

Or, ip = 62o 24′

When we look at our angle of refraction, we can observe that:

It is stated that ip plus ir equals 90 degrees.

The angle of refraction or ir = 90 – 62o 24′ as a result.

Our angle of refraction is therefore 27.6 o

Example 2: How much light passes through the air at Brewster’s angle when it leaves water (n = 1.33)?

Answer: Upon closer inspection of the question, we note that our n1 is already 1.33. As a result, by using the formula, we will obtain:

Brewster’s angle equals tan1(n2n1).

Brewster’s angle equals tan 1 (1.51.33)

Brewster’s angle is therefore 48.4°.

The Brewster’s angle is 48.4° as a result.

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