Multiple choice

When angle of incidence is equal to the critical angle, the angle of refraction is _____.

  1. 0°

  2. 90°

  3. 145°

  4. 180°
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

At the critical angle, the refracted ray grazes along the boundary between the two media, making an angle of 90° with the normal. This is the defining condition for total internal reflection - when the angle of incidence equals or exceeds the critical angle, light can no longer enter the second medium.

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