Reflection, refraction and diffraction of waves

Answer Key - Grade 11 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   A ray in air hits a clear liquid at 45° from the normal and refracts at 30° from the normal. What is the liquid's refractive index, to 2 decimals, Ari?

   1.41 n
2. 2.

   A ray in air hits a clear liquid at 60° from the normal and refracts at 40° from the normal. What is the liquid's refractive index, to 2 decimals, Bo?

   1.35 n
3. 3.

   A ray in air hits a clear liquid at 70° from the normal and refracts at 38° from the normal. What is the liquid's refractive index, to 2 decimals, Esme?

   1.53 n
5. 4.

   Kira doubles the ripple frequency in the same tank, so the wavelength halves. What is the first-minimum angle for the 4.0 cm gap now?

   • 60°, since doubling the frequency doubles the angle
   • 30°, the same as before, since the gap has not changed
   • 7°, since halving the wavelength halves the angle
   • 14°, the same as the 8.0 cm gap gave before
6. 5.

   With a wavelength of 3.0 cm, Luz wants the first minimum at 30°. What gap width is needed?

   Use the picture in question 4.

   • 3.0 cm
   • 6.0 cm
   • 12 cm
   • 1.5 cm
7. 6.

   A doorway 0.9 m wide casts a sharp light shadow. Milo says light does not diffract. Light's wavelength is 500 nm. Agree or disagree?

   • Disagree: light does diffract, but 500 nm is about two million times smaller than the doorway
   • Agree: a sharp shadow means light travels in straight lines, so it cannot diffract, whatever the gap
   • Disagree: light spreads a lot, but the spread is hidden by the brightness of the room
   • Agree: light diffracts through gaps narrower than the doorway, and this one is not narrow enough
8. 7.

   In one glass, n is 1.51 for red light and 1.53 for violet. Noah says red bends most on entering the glass, since it has the longest wavelength. Agree or disagree?

   • Agree: the longest wavelength means the largest change when light enters the glass
   • Agree: red is slower in glass because its frequency is lower than violet's
   • Disagree: violet slows down more in the glass, so it bends more toward the normal
   • Disagree: red and violet bend the same amount, because n is almost equal
9. 8.

   A diver 2.0 m below calm water looks up. The whole sky shows through a circle on the surface; the critical angle is 48.8°. What is the circle's radius, Ren?

   • 2.3 m
   • 1.8 m
   • 1.3 m
   • 1.5 m
10. 9.

    An ultrasound scanner must show details as small as 0.25 mm, so the wavelength must be no more than that. Sound in soft tissue travels at about 1540 m/s. What frequency is needed, Tala?

    • At least about 6.2 MHz
    • At least about 3.1 MHz
    • At least about 0.62 MHz
    • At least about 62 MHz
11. 10.

    A depth sounder assumes 1481 m/s, but sound in this seawater travels at 1500 m/s. An echo returns after 0.120 s. What does it read, and how far off is it, Zee?

    • It reads 90.0 m, which is correct
    • It reads 88.9 m, which is 1.1 m too deep
    • It reads 88.9 m, which is 1.1 m too shallow
    • It reads 177.7 m, which is 2.3 m too shallow