Thue/False (12 marks) __ 1. The universal wave equation can be used to calculate the amplitude of a wave. __ 2. When a student sends a positive pulse towards the free-end of a spring, the reflected pulse returns as a negative pulse. __ 3. The scientific musical scale is based on a frequency of 200 Hz , and each octave is twice the frequency of the octave before it. __ 4. The principle of superposition relates the three wave quantities of speed wavelength, and frequency. __ 5. The nodal point of a standing wave forms due to the continuous destructive interference of two waves at that point __ 6. The intensity of sound is could be measured in kilowatts per cubic centimetre __ 7. As the air temperature decreases, the speed of sound also decreases. __ 8. An object which completes 100 vibrations in 2.5 s produces sound audible to most humans. __ 9. In humans with healthy hearing, the audible frequencies range from 20 Hz to 20000kHz. __ 10. In general, sound travels most quickly in solids and most slowly in gases. __ 11. If tuning forks with frequencies of 512 Hz and 514 Hz are sounded at the same time, 10 beats will be heard in 5.0 s. __ 12. Decreasing the density of a vibrating string will increase its frequency.

1. **False.** The universal wave equation (v = fλ) relates wave speed, frequency, and wavelength, not amplitude.<br /><br />2. **False.** When a pulse reaches a free end, it reflects back with the same sign/polarity. A positive pulse reflects as a positive pulse.<br /><br />3. **False.** The standard musical scale is based on A4 = 440 Hz, with octaves doubling the frequency.<br /><br />4. **False.** The principle of superposition describes how waves combine when they overlap, not the relationship between speed, wavelength, and frequency (that's the universal wave equation).<br /><br />5. **True.** Nodes in standing waves are points of zero amplitude due to destructive interference.<br /><br />6. **False.** Sound intensity is typically measured in watts per square meter (W/m²) or decibels (dB).<br /><br />7. **True.** The speed of sound in air is proportional to the square root of the absolute temperature. Lower temperature means lower speed.<br /><br />8. **True.** 100 vibrations in 2.5 seconds is a frequency of 100/2.5 = 40 Hz. This falls within the typical human hearing range.<br /><br />9. **False.** The upper limit is 20,000 Hz (or 20 kHz), not 20,000 kHz.<br /><br />10. **True.** Sound generally travels fastest in solids, then liquids, and slowest in gases.<br /><br />11. **True.** The beat frequency is the difference in frequencies: |514 Hz - 512 Hz| = 2 Hz. This means 2 beats per second, so in 5 seconds there will be 2 beats/s * 5 s = 10 beats.<br /><br />12. **True.** Decreasing the density of a string (while keeping other factors constant) will increase its wave speed, and since frequency is proportional to wave speed, the frequency will also increase.<br />