Question

Ultrasound can be used to deliver energy to tissues for therapy. It can penetrate tissue to a depth approximately 200 times its wavelength. What is the approximate depth of penetration of ultrasound at a frequency of 5.0 MHz?

A. 0.29 mm
B. 1.4 cm
C. 6.2 cm
D. 17 cm

Answer 1

(C) 6.2 cm

Step-by-step explanation:

We are given that

Frequency of ultra sound,f=5.0 MHz=
`5* 10^6 Hz`

By using
`1MHz=10^6 Hz`

We know that speed of sound in human tissue,v=1540m/s

Let
`\lambda` be the wavelength of ultrasound .

Then, depth of penetration of ultrasound=
`d=200\lambda`

We have to find the approximate depth of penetration of ultrasound.

We know that

`\lambda=(v)/(f)`

Using the formula

`d=200* (v)/(f)=200* (1540)/(5* 10^6)`

`d=6.2* 10^(-2) m`

`d=6.2* 10^(-2)* 10^2=6.2* 10^(-2+2)=6.2* 10^0=6.2* 1=6.2 cm`

By using
`a^x\cdot a^y=a^(x+y)`

`10^0=1`

Option C is true.