Final answer:
The correct formula for calculating the wavelength of ultrasound is Option 1: λ = c/f, accounting for the speed of sound in a medium and the frequency of the wave.
Step-by-step explanation:
When determining the wavelength formula for ultrasound, the correct formula is Option 1: λ = c/f, where λ is the wavelength, c is the speed of sound in the medium, and f is the frequency. Ultrasound waves are mechanical waves that travel through media like air or human tissue, and their speed depends on the medium, not the speed of light. The relationship between wavelength and frequency for sound waves is given by the equation c = fλ, which can be rearranged to λ = c/f to find the wavelength given the frequency and the speed of sound in that particular medium.