Light And Sound
Visão Geral
Light lets you see the world, and sound lets you hear it, but both travel as waves, and both obey the same core rules when they bounce off surfaces or pass from one material into another. Understanding reflection, refraction and total internal reflection unlocks everything from fibre-optic broadband to the sparkle of a diamond.
In this topic you will apply the law of reflection, use Snell's law to calculate refractive index, find critical angles, and draw accurate ray diagrams. You will also explore how sound travels, how an oscilloscope reveals its frequency and amplitude, and why pitch and loudness depend on different wave properties.
Objetivos
- Know that light waves are transverse waves and that they can be reflected and refracted
- Use the law of reflection (the angle of incidence equals the angle of reflection)
- Draw ray diagrams to illustrate reflection and refraction
- Investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms
- Know and use the relationship between refractive index, angle of incidence and angle of refraction: n = sin i / sin r
- Investigate the refractive index of glass, using a glass block
- Describe the role of total internal reflection in transmitting information along optical fibres and in prisms
- Explain the meaning of critical angle c
- Know and use the relationship between critical angle and refractive index: sin c = 1 / n
- Know that sound waves are longitudinal waves that can be reflected and refracted
- Know that the frequency range for human hearing is 20-20,000 Hz
- Investigate the speed of sound in air
- Understand how an oscilloscope and microphone can be used to display a sound wave
- Investigate the frequency of a sound wave using an oscilloscope
- Understand how the pitch of a sound relates to the frequency of vibration of the source
- Understand how the loudness of a sound relates to the amplitude of vibration of the source
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Nota de Aula
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- When a ray of light passes from air into glass, it bends: A) Away from the normal B) Towards the normal C) Along the normal D) It does not change direction Answer: B
- The critical angle of a material with a refractive index of 1.4 is: A) 35.3 degrees B) 41.8 degrees C) 45.6 degrees D) 48.6 degrees Answer: C
- Sound waves are: A) Transverse waves that can travel through a vacuum B) Longitudinal waves that can travel through a vacuum C) Transverse waves that need a medium D) Longitudinal waves that need a medium Answer: D
- The frequency range of human hearing is: A) 2 Hz to 2000 Hz B) 20 Hz to 20 000 Hz C) 200 Hz to 200 000 Hz D) 2000 Hz to 20 000 Hz Answer: B
- On an oscilloscope trace, a louder sound would show: A) More waves on the screen B) Fewer waves on the screen C) Taller waves D) Shorter wavelength Answer: C
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Secção do manual
Refraction
Explain refraction at media boundaries, predict the path of light after passing through a boundary (Snell’s law), describe the index of refraction of materials, explain total internal reflection, and describe applications of refraction and total internal reflection
"Physics: Refraction" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/16-2-refraction. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Secção do manual
Reflection
Explain reflection from mirrors, describe image formation as a consequence of reflection from mirrors, apply ray diagrams to predict and interpret image and object locations, and describe applications of mirrors
"Physics: Reflection" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/16-1-reflection. Access for free at https://openstax.org/books/physics/pages/1-introduction
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