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Bond [772]
4 years ago
8

A beam of 1.0 MHz ultrasound begins with an intensity of 1000 W/m². After traveling 12 cm through tissue with no significant ref

lection, the intensity is about
A. 750 W/m²
B. 500 W/m²
C. 250 W/m²
D. 125 W/m²
Physics
1 answer:
Ksenya-84 [330]4 years ago
4 0

Answer:

Option C

Explanation:

Given:

- Depth of tissue d = 12 cm

- frequency of ultrasound f = 1 MHz

- Input Intensity I_i = 1000 W/m^2

- attenuation coefficient soft tissue a = 0.54

Find:

- Out-put intensity at the required depth

Solution

- The amount of attenuation in (dB) with the progression of depth is given by:

                                     Attenuation = a*f*d

                                     Attenuation = 0.54*12*1

                                     Attenuation = 6.48 dB

- The relation with attenuation and ratio of input and output intensity is given by:

                                     Attenuation = 10*log_10 (I_i / I_o)

                                     6.48 dB = 10*log_10 (I_i / I_o)

                                      I_i / I_o = 10^(0.648)

                                      I_o = 1000 / 10^(0.648)

                                      I_o = 225 W/m^2

- Hence the answer is option C:  I_o = 250 W/m^2  

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6 0
3 years ago
The force of friction occurs primarily because:
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Answer:

B

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3 0
3 years ago
Tammy leaves the office, drives 26 km due
fredd [130]

Answer:

72.98 km

Explanation:

Her displacement is simply the distance from her final position to her initial position.

Now, I've drawn and attached a triangle diagram to depict this her movement.

Point O is her initial starting point.

Point A is the first point she gets to after travelling north while point B is the final point after travelling north east.

From the triangle, the displacement will be the distance OB which is denoted by x and can be solved from cosine rule.

Thus;

x² = 62² + 26² - 2(62 × 26)cos 120

x² = 4520 + 806

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4 0
3 years ago
A car traveling at 20 m/s starts to decelerate steadily. It comes to a complete stop in 7 seconds. What is it’s acceleration?
Yuki888 [10]
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6 0
3 years ago
A heat engine has a maximum possible efficiency of 0.780. If it operates between a deep lake with a constant temperature of-24.8
Volgvan

Answer : The temperature of the hot reservoir (in Kelvins) is 1128.18 K

Explanation :

Efficiency of carnot heat engine : It is the ratio of work done by the system to the system to the amount of heat transferred to the system at the higher temperature.

Formula used for efficiency of the heat engine.

\eta =1-\frac{T_c}{T_h}

where,

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T_h = Temperature of hot reservoir = ?

T_c = Temperature of cold reservoir = -24.8^oC=273+(-24.8)=248.2K

Now put all the given values in the above expression, we get:

\eta =1-\frac{T_c}{T_h}

0.780=1-\frac{248.2K}{T_h}

T_h=1128.18K

Therefore, the temperature of the hot reservoir (in Kelvins) is 1128.18 K

8 0
3 years ago
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