Three of these are wrong. Find the one that holds.

Exercise and reference answers

Questions

1. Question

   Three of these statements about total internal reflection are false.

   Choices

   1. Item

      It needs denser to rarer travel

      Correct

      Yes

   2. Explanation

      The direction is the other way.

      Item

      It happens rarer to denser

   3. Explanation

      It occurs ABOVE the critical angle.

      Item

      It occurs below the critical angle

   4. Explanation

      90° is the REFRACTED angle at the critical angle itself.

      Item

      It needs the angle to be exactly 90°

2. Question

   Three of these statements about lens power are false.

   Choices

   1. Item

      P equals 1/f with f in metres

      Correct

      Yes

   2. Explanation

      Power is the reciprocal, not the focal length.

      Item

      P equals f

   3. Explanation

      1 D is 1 m⁻¹, an inverse metre.

      Item

      1 D equals 1 metre

   4. Explanation

      Its focal length is negative, so its power is too.

      Item

      A diverging lens has positive power

Explanation