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.

   The table was taken with a 2.0 cm wavelength. What does it show about the gap, Jun?

   • Widening the gap toward the wavelength spreads the waves more, as the angle column shows
   • Narrowing the gap toward the wavelength spreads the waves more, up to 90° at 2.0 cm
   • The spread depends on the size of the gap alone, not on the wavelength, as this table shows
   • A gap narrower than 2.0 cm stops the waves completely, so there is no angle for it
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.

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

   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
8. 7.

   Pia says the angle in the liquid is always the same fraction of the angle in air. Does the table support the claim?

   • No: the angle ratio falls from 0.75 to 0.67, while the sine ratio stays near 1.33
   • Yes: the angle in the liquid rises as the angle in air rises
   • No: the angles rise by the same step each time, so they cannot be a fraction
   • Yes: the angle ratio is 0.75 at 20° and about the same at 60°
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?

   • 1.3 m
   • 1.5 m
   • 1.8 m
   • 2.3 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 3.1 MHz
    • At least about 6.2 MHz
    • At least about 62 MHz
    • At least about 0.62 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 88.9 m, which is 1.1 m too shallow
    • It reads 90.0 m, which is correct
    • It reads 177.7 m, which is 2.3 m too shallow
    • It reads 88.9 m, which is 1.1 m too deep