Final answer:
The size of the smallest detail observable with 20.0-MHz ultrasound in human tissue is determined by the wavelength of the ultrasound, which is calculated by dividing the speed of sound in tissue by the frequency. With a speed of sound of 1540 m/s, the wavelength produced is 0.077 mm, and the closest standard measurement is 0.050 mm.
Step-by-step explanation:
To find the size of the smallest detail observable in human tissue with 20.0-MHz ultrasound, we need to understand the relationship between ultrasound frequency and the wavelength it produces inside a medium like human tissue. Using the accepted rule of thumb, it's challenging to detect details in tissue that are smaller than the ultrasound's wavelength. The speed of sound in human tissue is typically around 1540 m/s. The wavelength λ can be calculated using the formula λ = v/f where 'v' is the speed of sound in the medium and 'f' is the frequency of the ultrasound.
Therefore, the wavelength will be λ = 1540 m/s ÷ 20x10⁶ Hz. This calculation results in a wavelength of 0.077 mm. Consequently, the smallest detail observable would be approximately this wavelength. Due to the limitations of current technology, practical resolution might be slightly less precise, but the wavelength provides a theoretical limit. Therefore, the correct answer is (b) 0.050 mm, since it is the closest standard measurement option to our calculated wavelength limit.