Reflection, refraction and diffraction of waves

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   A ray in air (n = 1) meets water (n = 1.33) at 40° from the normal. What is its angle from the normal in water, to the nearest degree, Ari?

   29 °
2. 2.

   A ray in air (n = 1) meets glass (n = 1.5) at 50° from the normal. What is its angle from the normal in glass, to the nearest degree, Bo?

   31 °
3. 3.

   Light of wavelength 500 nm passes through a single slit 2.0 μm wide. The first dark band is at sin θ = λ ÷ width. At what angle is it, Kira?

   • 0.25°
   • 14°
   • 29°
   • 76°
4. 4.

   Radio waves of wavelength 3 m bend round a hill 50 m wide, but light of wavelength 500 nm does not. Which explanation fits, Luz?

   • Radio waves are mechanical waves, which can bend round solid hills in a way light cannot
   • The hill is only about 17 times the radio wavelength, but millions of times the light's
   • Radio waves carry more energy than light, so they push round the hill
   • Light is too fast to bend round a hill, however wide the hill is
5. 5.

   A ray inside glass (n = 1.50) hits the glass-air surface at 45° from the normal. The critical angle is 41.8°. What happens, Milo?

   • Half reflects and half passes into air
   • It passes into air, bending away from the normal
   • All the light reflects back into the glass
   • It passes into air, bending toward the normal
6. 6.

   A ray inside the same glass (n = 1.50, critical angle 41.8°) hits the glass-air surface at 38° from the normal. What happens, Noah?

   • Most of it passes into air, bending away from the normal
   • It passes into air, bending toward the normal
   • It passes into air without bending, since 38° is a small angle
   • Everything reflects back into the glass, since the surface acts like a mirror
7. 7.

   An optical fiber has a core with n = 1.48 and cladding with n = 1.46. What is the critical angle at the core-cladding boundary, from the normal, Pia?

   • 80.6°
   • 47.5°
   • 42.5°
   • 9.4°
8. 8.

   Sound in air meets the surface of calm water, where sound is faster. How does the sound that enters the water bend, Ren?

   • Away from the normal
   • It does not bend, because sound is not light
   • Along the surface of the water
   • Toward the normal, like light entering glass
9. 9.

   Sound in 20 °C air (343.3 m/s) meets calm fresh water (1481 m/s). Above what angle from the normal is it totally reflected, Tala?

   • About 0.23°
   • About 77°
   • About 13°
   • About 4.3°
10. 10.

    A sonar pulse returns from a school of fish after 0.060 s in water at 1481 m/s. How far below the boat is the school, Zee?

    • About 22 m
    • About 89 m
    • About 44 m
    • About 10 m