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When a person sings, their vocal chords vibrate - Leaving Cert Physics - Question 10 - 2022
Question 10
When a person sings, their vocal chords vibrate. These vibrations travel through the air to the listener's ears. (i) Sound is an example of a mechanical wave which ... show full transcript
Worked Solution & Example Answer:When a person sings, their vocal chords vibrate - Leaving Cert Physics - Question 10 - 2022
Step 1
Sound is an example of a mechanical wave which therefore needs a medium to travel through. Describe an experiment to show that sound is a mechanical wave.
Answer
To demonstrate that sound is a mechanical wave, we can conduct a simple experiment using a bell jar.
Apparatus:
- A bell jar
- A sound source (such as a tuning fork)
- A vacuum pump
Method:
- Place the sound source inside the bell jar.
- Ensure that the jar is sealed properly.
- Gradually pump out the air using the vacuum pump.
Observation: As the air is removed, the sound from the tuning fork will diminish until it is inaudible when a vacuum is achieved. This shows that sound requires a medium (air) to travel, confirming it is a mechanical wave.
Step 2
Sound is also an example of a longitudinal wave. What is a longitudinal wave?
Answer
A longitudinal wave is one where the particle displacement is parallel to the direction of wave propagation. In simpler terms, as the wave moves through the medium, the particles move back and forth in the same direction as the wave travels.
Step 3
A doorway may cause a sound wave to diffract but it will not cause a light wave to do so. Explain why.
Answer
Sound waves are low-frequency waves and have longer wavelengths compared to light waves. When sound waves encounter an obstacle, such as a doorway, their longer wavelengths can bend around the edges, leading to diffraction. In contrast, light waves have much shorter wavelengths and cannot bend as easily around obstacles, thus they do not undergo diffraction in the same conditions.
Step 4
Describe an experiment to show that sound waves undergo interference.
Answer
To demonstrate interference of sound waves, we can use two speakers emitting the same sound.
Apparatus:
- Two speakers
- A sound generator (to produce a consistent frequency)
Method:
- Position the two speakers a certain distance apart in an open area.
- Play the same sound through both speakers simultaneously.
- Walk between the speakers to observe the sound levels.
Observation: You will notice spots of increased loudness and decreased loudness (nodal points) as you walk, indicating areas of constructive and destructive interference of the sound waves.
Step 5
Sound waves do not undergo polarisation but light waves do. What is meant by polarisation?
Answer
Polarisation refers to the orientation of the oscillations of a wave. For light waves, which are transverse, polarisation occurs when the oscillations are restricted to a particular direction in the plane perpendicular to the direction of wave propagation. In contrast, sound waves are longitudinal and the oscillations occur in the same direction as the wave travels, so they cannot be polarised.