A monochromatic ray of light is incident on a medium at an angle of 60°. The reflecting rays is found to be completely polarized. Then the refractive index of the medium is nearly

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ALP CBT 2 Physics and Maths Previous Paper 6 (Held On: 22 Jan 2019 Shift 3)
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  1. 1.33
  2. 1.50
  3. 1.73
  4. 1.41

Answer (Detailed Solution Below)

Option 3 : 1.73
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CONCEPT:

Polarizing angle: The angle of incidence at which a beam of unpolarized light falling on a transparent surface is reflected as a beam of completely plane polarised light is called polarizing or Brewster angle. It is denoted by ip.

Brewster's law: It states that when a ray is passed through some transparent medium having refractive index μ at any particular angle of incidence, the reflected ray is completely polarized; and the angle between reflected and refracted ray is 900.

 μ = tan θB 

Where μ = refractive index and θB is Brewster's angle or polarizing angle (ip).​

CALCULATION:

Given that:

The angle of incidence (ip) = 60°

From Brewster’s law, the polarization angle,

So refractive index (μ) = 1.73

Hence option 3 is correct.

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