iGCSE Physics (0625) 3.4 Sound-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
The diagram illustrates the limits of the human auditory system and the start of the ultrasound region.
The typical range of audible frequencies for a healthy human ear is approximately $20\text{ Hz}$ to $20000\text{ Hz}$ ($2 \times 10^1\text{ Hz}$ to $2 \times 10^4\text{ Hz}$).
Ultrasound is defined specifically as sound with a frequency higher than the upper limit of human hearing, which is $20\text{ kHz}$ or $20000\text{ Hz}$.
The horizontal axis uses a logarithmic scale to represent these numerical values, which correspond to the number of oscillations per second.
Therefore, the characteristics being measured are frequencies, and the standard unit for frequency is the Hertz ($\text{Hz}$).
Options A, C, and D refer to spatial or temporal properties that do not define the auditory boundaries shown.
▶️ Answer/Explanation
Detailed solution:
In longitudinal waves, particles vibrate parallel to the direction of wave travel. Diagram 2 represents sound waves in air, which are always longitudinal as they consist of compressions and rarefactions. Diagram 4 shows a spring being pushed and pulled horizontally, creating vibrations parallel to the energy transfer. Conversely, water waves (Diagram 1) and waves on a rope (Diagram 3) are transverse, where vibrations occur at $90^\circ$ to the direction of propagation. Therefore, only examples 2 and 4 describe longitudinal motion.
▶️ Answer/Explanation
Detailed solution:
Sound waves are longitudinal waves that propagate through the vibration of particles in a medium.
Because sound relies on these particle-to-particle interactions, it requires a physical medium—solid, liquid, or gas—to travel.
In a vacuum, there are no particles present to vibrate and transmit the energy of the sound wave.
Options A, B, and D contain air, carbon dioxide, and water respectively, all of which act as mediums for sound.
Since a vacuum lacks any matter, the sound from the loudspeaker cannot be transmitted to the student’s ears.
Therefore, the student will not hear a sound from the jar containing a vacuum.