Question

(a) Find the size of the smallest detail observable in human tissue with 22.5 MHz ultrasound. Incorrect: Your answer is incorrect. mm (b) Is its effective penetration depth great enough to examine the entire eye (about 3.00 cm is needed)? Yes No What is the effective penetration depth? cm (c) What is the wavelength of such ultrasound in 0°C air? µm

Answer 1

(a) The size of the smallest detail observable in human tissue which is given as :

we know that,              v = f                         

where, v = speed of sound in tissue = 1540 m/s

f = ultrasound frequency = 22.5 x 10⁶ Hz

inserting the values in above eq.

(1540 m/s) = (22.5 x 10⁶ Hz)

= 68.4 x 10^-6 m

= 0.068 mm

(b) No, its effective penetration depth great enough to examine the entire eye (about 3 cm is needed).

The effective penetration depth will be given as :

d = 500

d = (500) (0.068 mm)

d = 34 mm

d = 0.034 m  

d = 3.4 cm

(c) The wavelength of such ultrasound in 0 ⁰C air which is given as :

using an equation,      = v / f           

where, v = speed of cound in air = 340 m/s

f = ultrasound frequency = 22.5 MHz

inserting these values in above eq.

= (340 m/s) / (22.5 x 10⁶ Hz)

= 15.1 x 10^-6 m

= 15.1 m