Submarine echo physics problems

In summary: Also, I'm not sure how to use the given equation to solve for the object's depth.In summary, the problem involves a submarine on the ocean surface receiving a sonar echo at an angle of 20 degrees above the horizontal after 2.32 seconds. The equation to use is (2pi/lambda) * (delta of L) and the solution involves finding the total distance traveled by the sound using d = (v * t * sin(20)) / (sin(20) + 1). The answer may vary depending on the speed of sound in water.
  • #1
akd28
5
0

Homework Statement


A submarine on the ocean surface gets a sonar echo indicating an underwater object. The echo comes back at an angle of 20* above the horizontal and the echo took 2.32s to get back to the submarine. What is the object's depth?

Homework Equations


delta of theta = (2pi/lambda) * (delta of L)

I = (P)/(4piR^2) and (I2/I1) = (R1/R2)^2

The Attempt at a Solution


I really have no idea where to begin this problem. I can't really visualize it...if the submarine is on the ocean's surface and emits a sonar signal, shouldn't the echo be coming up from under the submarine vertically? Why is it 20* above the horizontal? I tried drawing a diagram but I don't know what it should look like with the information given. Also, I have no idea what equation would be best to use either. (I have more equations, I just thought that these would be the most helpful for the problem.)



Homework Statement


A person has a hearing loss of 30dB for a particular frequency. What is the sound intensity that is heard at this frequency that has an intensity of the threshold of pain?

Homework Equations


same I equations as above and B = 10log(I/Io)

Ip = 1.0W/m^2

The Attempt at a Solution


Here is what I did:

log (I / 1.0W/m^2) = 3B
I = 10^3 W/m^2

Am I totally off on what the question is asking me to do?

THANKS!
 
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  • #2
Ok, for the first one...

I'm not quite sure if what I did was correct, but I'll give you my two cents.

http://img184.imageshack.us/img184/51/subto4.gif [Broken]

So from that drawing, you can see kind of how I pictured it. If that's the case, you know v = 343 m/s (speed of sound in air...you'll probably need to speed of sound in water for this problem which I don't know). You also know t = 2.32 s, and that the angle is 20 degrees.

I figured that the distance down was d, and the hypotenuse was d/sin(20) by trig. Adding these two numbers, you find the total distance traveled by the sound to be d + d/sin(20), or what I thought was easier, ( d (sin(20) + 1 ) )/sin(20). Since you can assume that the acceleration is zero for sound, you can simply use d = vt.

Your equation should look something similar to:

d = (v * t * sin(20)) / (sin(20) + 1)

I got 202.8 m using the speed of sound in air. Using the correct value for the speed of sound in water should change your answer...But again, I have no idea if I thought of the question correctly either.
 
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  • #3
Your figure makes sense but the problem states that the echo comes back at an "angle 20* ABOVE the horizontal". That's the part that confuses me.
 

1. What is submarine echo physics?

Submarine echo physics is the study of sound propagation and reflection in the underwater environment. It involves understanding how sound waves behave in water and how they interact with different objects, such as submarines and other marine vessels.

2. How do submarines use echo physics?

Submarines use echo physics for various purposes, such as navigation, communication, and detecting other underwater objects. By emitting sound waves and analyzing the echoes that bounce back, submarines can determine their location, avoid obstacles, and communicate with other vessels.

3. What factors affect submarine echo physics?

Several factors can affect submarine echo physics, including the temperature, salinity, and depth of the water. Other factors include the shape and size of the submarine, the frequency and amplitude of the sound waves, and the presence of other objects or marine life in the water.

4. What are the potential problems with submarine echo physics?

One potential problem with submarine echo physics is the interference of sound waves from other sources, such as marine animals or human-made noise. This can make it challenging to accurately interpret the echoes and can affect the submarine's ability to navigate or communicate effectively.

5. How do scientists study submarine echo physics?

Scientists use various tools and techniques to study submarine echo physics, including sonar technology, hydrophones, and computer simulations. They also conduct experiments and collect data in different underwater environments to better understand the behavior of sound waves in the ocean.

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