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Difficulty: EasyWave Phenomena: Reflection, Refraction, Interference, Diffraction, and Polarization

Under which of the following conditions will total internal reflection occur when light encounters the boundary between two transparent media?

  1. When light travels from a medium of higher refractive index to one of lower refractive index at an angle of incidence greater than the critical angle.Answer
  2. B
    When light travels from a medium of lower refractive index to one of higher refractive index at an angle of incidence greater than the critical angle.
  3. C
    When light travels from a medium of higher refractive index to one of lower refractive index at an angle of incidence less than the critical angle.
  4. D
    When light travels from a medium of lower refractive index to one of higher refractive index at normal incidence.

Answer

Total internal reflection occurs when light travels from a medium of higher refractive index to a medium of lower refractive index at an angle of incidence greater than the critical angle.
Total internal reflection takes place only when light moves from an optically denser medium (higher refractive index) into an optically less dense medium (lower refractive index), and the angle of incidence at the interface is greater than the critical angle for the two media.

Step-by-Step Solution

1
Identify the optical density requirement for total internal reflection
Light must travel from an optically denser medium (higher refractive index n1n_1) toward an optically rarer medium (lower refractive index n2n_2).
This condition ensures that the light refracts away from the normal into the second medium.
2
Identify the angular requirement at the interface
The angle of incidence ii must be strictly greater than the critical angle θc\theta_c (sin⁡θc=n2n1\sin\theta_c = \frac{n_2}{n_1}).
When i>θci > \theta_c, no light can refract into the second medium, resulting in total reflection back into the initial medium.

Key Concept

Conditions for Total Internal Reflection
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Topics

Wave Phenomena: Reflection, Refraction, Interference, Diffraction, and Polarization

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