I figured out that when I aim a laser beam on my window at an arbitrary angle, the total internal reflection doesn't occur whatsoever. What's more, the refracted beam seems to be pretty intense. It was basically done in normal conditions, just lazer and glass window, so diffraction or something like that cannot be the answer. Can anyone explain this?


1 Answer 1


Total internal reflection can occur when light is in an optically more dense medium, about to enter a less dense medium. It could occur going from glass to air, but not the other way around.

The angle of incidence must also be greater than the critical angle.

  • $\begingroup$ Dang, I feel so ashamed 😂. How could I think of that stupid question... Sorry for wasting your time, but thank you for the answer. My brain must've been completely turned off then $\endgroup$
    – Sgg8
    Nov 24, 2021 at 5:48
  • 1
    $\begingroup$ @ Ostap, it's not wasted anyone's time, others may not realise...anyway here is another you could ask if you feel like it. When the light approaches at the critical angle, diagrams often show it continuing at 90 degrees, i.e. along the interface between of the two media. But there is the principle of 'reversibility of light'. Going the other way, how would light, traveling along the interface, know when to suddenly divert it's direction? $\endgroup$ Nov 24, 2021 at 8:40

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