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Grade 12Wave Optics

the angle of polarization for any mediun is 60o .what will the critical angle for this ?

Profile image of krishna priya
9 Years agoGrade 12
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1 Answer

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ApprovedApproved Tutor Answer1 Year ago

To determine the critical angle for a medium where the angle of polarization is 60 degrees, we can use Snell's Law and the concept of Brewster's angle. The angle of polarization, also known as Brewster's angle, is the angle at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection. This angle is related to the refractive indices of the two media involved.

Understanding the Relationship

The critical angle is the angle of incidence above which total internal reflection occurs when light travels from a denser medium to a less dense medium. The relationship between Brewster's angle (θ_B) and the refractive indices can be expressed as:

  • tan(θ_B) = n2/n1

Where:

  • θ_B is Brewster's angle (60 degrees in this case).
  • n1 is the refractive index of the first medium (denser).
  • n2 is the refractive index of the second medium (less dense).

Calculating the Refractive Indices

Using the tangent function, we can find the ratio of the refractive indices:

  • tan(60°) = √3 ≈ 1.732

This means:

  • n2 = 1.732 * n1

Finding the Critical Angle

The critical angle (θ_c) can be calculated using the formula:

  • sin(θ_c) = n2/n1

Substituting the expression we found for n2:

  • sin(θ_c) = (1.732 * n1) / n1 = 1.732

However, since the sine function cannot exceed 1, we need to adjust our understanding. The critical angle can only be calculated when n1 is greater than n2. Thus, we need to consider the scenario where n1 is the refractive index of the denser medium and n2 is that of the less dense medium.

Revising the Calculation

Let’s assume n1 is the refractive index of the denser medium and n2 is the refractive index of the less dense medium. The correct relationship for the critical angle is:

  • sin(θ_c) = n2/n1

Since we know that:

  • n2 = n1 / √3

We can substitute this into the critical angle formula:

  • sin(θ_c) = (n1 / √3) / n1 = 1 / √3

Final Calculation

Now, we can find the critical angle:

  • θ_c = sin⁻¹(1 / √3) ≈ 35 degrees

Therefore, the critical angle for a medium with an angle of polarization of 60 degrees is approximately 35 degrees. This means that if the angle of incidence exceeds this critical angle, total internal reflection will occur, and no light will pass into the second medium.