Answer 1

(a) Given:
Frequency of ultrasonic wave f = 4.5 MHz = 4.5 × 10⁶ Hz
Velocity of air v = 340 m/s 
Speed of sound in tissue = 1.5 km/s
Wavelength λ = ?
As we know, \[v = f\lambda\]

\[\therefore   \lambda = \frac{340}{4 . 5 \times {10}^6}\] 

\[ \Rightarrow \lambda = 7 . 6 \times  {10}^{- 5}   m\]

(b)   Velocity of sound in tissue v_tissue= 1500 m/s

\[\lambda = \frac{v_{tissue}}{f}\] 

\[ \Rightarrow   \lambda = \frac{1500}{4 . 5 \times {10}^{- 6}} \text{ m }\] 

\[ \Rightarrow   \lambda = 3 . 3 \times  {10}^{- 4}  \text{ m }\]