If sand and water is placed in between tin and a metal detector, then the metal detector will have to come closer for it to detect the metal. This is because the electromagnetic waves will be reduced as they travel through the water and sand to the metal and the metal’s electromagnetic field will be weaker.

 

I will do two experiments in this project. The first one is called the Different Metals Test. In this test I will test different metals for how easily they can be picked up by a metal detector. I didn't include a hypothesis for this test because it was to prove the reliability of the metal detector so that I could confidently say the results in the second test were accurate. The second test is called Sand and Water Test and will test metal detectors ability to detect a large piece of tin that is buried under sand and water. This is my main test because it will prove whether metal detectors work well enough under water to hold up to the task of finding the bombs.

Problem Statement

Between 1918 and 1964, Switzerland dumped their surplus, faulty and expired bombs into lakes. They decided to do this because it was considered a safe way to remove them. Lots of places have gotten rid of their ammunition by dumping it into the lakes.

They were dropped into many lakes but some of the worst include Thun, Brienz, Neuchatel, Lucerne. The government decided to hold a contest and open it to the public to find a solution. The contest was put out to see if the public could help give them a foundation or start on how to do this. The contest ended on February 6 2025 and the winners are announced in April.

The bombs need to be brought to the surface because the corroding metal and the chemicals in the bombs are contaminating the water. There is also the risk that they will explode and if one explodes they all will. This makes it unsafe for people who work in and around the lakes. 

As I was trying to figure out how I could do this I realized that first I would need a way to know where the bombs were in the lake. I decided to test a metal detector to see if it could reliably find the bombs even when water and sand are present.

Metal detectors

A metal detector is a device that can detect certain types of metal. The metals that work best with metal detectors are ferrous, which are metals that contain iron, because they are highly magnetic. 

Metal detectors work by sending an electromagnetic field in all directions. When the electromagnetic field comes in contact with a piece of metal, the metal will be energised and create its own electromagnetic field. This field is also sent in all directions. If it's strong enough to reach the metal detector, the search coils will pick it up and notify you that there is metal in the direction your metal detector is pointing.

What are electromagnetic waves

Electromagnetic waves are waves that have electric waves going vertically and magnetic waves going horizontally. These waves are very important in our life. This is because electromagnetic waves are light waves. 

Electromagnetic spectrum

We can only see a very small portion of the electromagnetic spectrum. What we can see is called visible light. To the left is inferred and to the right is ultraviolet light. Past that are x-ray and gamma rays. These rays can be dangerous as they can go through the skin but also very helpful in hospitals and airports. When the wavelength increases you move to the left on the spectrum. Radio and microwaves have the largest wavelength and are used in things like cooking, radar, television and radios. As the wavelengths decrease you move to the right of the spectrum. As you move right the waves become more dangerous. X-rays can view inside things including skin and are dangerous. Gamma rays are used to kill cancer cells.

Amplitude is the height of an electromagnetic wave from the resting point. More energy will have higher amplitude and a less energy will have lower amplitude. The peak is the highest part of the wave and the trough is the lowest.

Definitions

Electromagnetic field - An electric and magnetic field.

Electromagnetic wave - when electric field is disrupted, it disturbs the magnetic field which affects the electric field making it oscillate creating an electrmagnetic wave.

Electromagnetic energy/radiation - light, energy and magnetic energy traveling and creating an electromagnetic field.

 

Frequency 

The Electromagnetic spectrum is when light has a higher frequency resulting in a shorter wavelength. Longer wavelengths are to the left on the spectrum and shorter wavelengths to the right. Frequency is the amount of waves that pass in a given time.

Parts of a Metal detector	What they do
Control box	Holds technology
Search coils	Transmits and receives electromagnetic fields
Target	Any metal object
Unwanted target	Ferrous  Non-ferrous
Received electromagnetic field	Generated by energised metal object
Target response	Sound when object is found
Electromagnetic field	What is sent in all directions and what is re-transmitted by energised metal

I did more research after the experiment to determine what other tools could be used.

Sonar

Sonar is a type of underwater mapping that uses sound waves. Sonar uses sound to measure the distance from the surface of the water to the body of the water's floor. In this way we can create an accurate map of the terrain at the bottom of oceans and lakes.

Sonar uses sound to do this. The sonar device sends down a loud sound called a ping. The ping is then reflected like an echo back up and the device catches it. Sonar uses the time interval from the time the sound is made to when it is returned and the strength of the returned noise to determine the distance. Using this method navies search for enemy submarines and other things posing a risk underwater. Sonar is also used by scientists to better understand the ocean and other bodies of water.

Sonar is dangerous for sea life and can be very harmful to the environment. It can also harm humans so sonar is not always the best option. Sonar is amazing at mapping the bottom of bodies of water but can be dangerous for wildlife.

 

Different Metals Test

Manipulated: changed the metal.

Responding: the distance the metal detector is when it begins going off.

Controlled:

Type of metal detector	Didn’t use another type of metal detector.
Shape and size of metals	Used the same piece throughout the experiment.
Container tested on	Didn’t change the container.
Location tested in	Left setup exactly how it was and didn’t move it.
Measuring tape	Used the same one in all trials.
Same metal in every trial	Didn’t change metal during a trial.

Sand and Water Test

Manipulated: adding a litre of sand and water between metal sample and metal detector

Responding: the distance the metal detector is when it begins going off

Controlled:

Type of metal detector	Didn’t use another type of metal detector.
Amount of water	Measured exactly a litre each test and didn’t change it between trials.
Amount of sand	Measured exactly a litre each test and didn’t change it between trials.
Type of metal	Used the same piece throughout the experiment.
Shape and size of metal	Used the same piece throughout the experiment.
Container tested in	Didn’t change the container.
Location tested in	Left setup exactly how it was and didn’t move it.
Measuring tape	Used the same one in all trials.

 

If any of these items changed it could result in inaccurate data and we wouldn’t be able to say with confidence what changed the results.

          Different Metals Test 

1. Find materials
2. Set up 2 chairs with their backs facing towards the middle
3. Attach long piece of wood across the tops of the chairs
4. Mark a dot roughly in the middle of the long piece of wood
5. Attach your fabric tape measure to the metal detector so that the metal detector is facing down
6. Drape the fabric tape measure over the long piece of wood with one end of the tape measure on one side and the metal detector on the other
7. Place your plastic container (or wooden block) under the metal detector
8. Record the initial measurement when the metal detector is lowered all the way down to the container (record the number at the dot you marked on the long piece of wood)
9. Put your choice of metal on the container
10. Lower the metal detector until it starts going off and record the second measurement
11. Subtract the second measurement from the initial measurement. This equals the distance between the metal and the point the metal detector goes off.
12. Repeat this process with different types of metals and complete multiple trials

    Sand and Water Test

13. Repeat steps one to eight from the Different Metals Test
14. Select one type of metal for all trials 
15. Place the metal in the bottom of the plastic water jug
16. Lower the metal detector until it starts going off and take second measurement (this is the control)
17. Then fill the plastic container with your decided amount of sand, lower the metal detector again and take a new second measurement.
18. Repeat Step 17 with water only and then repeat again with sand and water.
19. Subtract the second measurement from the initial measurement. This equals the distance between the metal and the point the metal detector goes off.
20. Complete multiple trials.                                                                                                                                       

 

Test Notes

• The set up of the tests was done with as much wood as possible so that I could eliminate the chances of the metal detector picking up another metal.
• The block of wood underneath the plastic container was also to stop it from picking up other metal in the floor.
• The reason the piece of tin that I used in the sand and water test was so much larger than all the other metals was because the larger the piece of metal the farther away the metal detector could be from it giving us more room to add sand and water.

Different Metals Test

	Trial 1	Trial 2	Trial 3	Trial 4	Average
Copper	6.7	7.1	7	6.9	6.9
Nickel	4.7	4.9	4.9	4.9	4.9
Mild Steel	5.0	4.6	4.7	4.9	4.8
Stainless Steel*	0.0	0.0	0.0	0.0	0.0
Bronze	5.9	6	5.8	5.6	5.8
Brass	6.5	6.6	6.5	6.1	6.4
Aluminum	7.0	6.7	6.9	6.8	6.9
Zinc	7.0	7.0	6.8	6.3	6.8

Sand and Water Test 

	Trial 1	Trial 2	Trial 3	Trial 4	Average
Tin only (Control)	12.8	12.4	12.4	12.4	12.5
Sand	12.2	12.3	12.3	12.2	12.3
Water	12.7	12.4	12.6	12.4	12.5
Sand and Water	12.7	12.6	13.0	11.7	12.5

 

Different Metals Test

Sand and Water Test

Diifferent Metals Test

This test proved that copper and aluminum are the easiest metal to detect using a metal detector. Copper and aluminum could be farthest away from the metal detector when it was set off (the distance was 6.9 cm away). In contrast my type of stainless steel didn’t set off the metal detector even when it was directly on top. The other six metals fell between 4 cm and 6 cm. Although this sounds insignificant, it still showed that the distance changed with each metal. I also observed that often the measurement would be slightly greater distance in the first trial and then about 1 cm closer for the rest of the trials. In each trial I observed that the results were within a 1cm of each other. This further indicates the metal detector was reliable because the results were fairly consistent. If the results were all over the place, it would mean that one of the controlled variables had changed. In this experiment, large variation would likely be due to the metal detector, as the other controlled variables were easier to control. 

Sand and Water Test

The average of water and sand (the test with the most density), performed exactly the same as the control. They both averaged 12.5 cm between the metal and the metal detector. This data proved that sand and water do not affect electromagnetic waves. This is because there was almost no difference compared to the tin only (control). The averages show that the elements tested don’t affect electromagnetic waves because sand and water or water by itself were 12.5cm the same distance as the control. Sand was 0.2cm closer. Each test’s, control, sand, water, and sand and water, trials stayed within a cm of eachother with the tens place fluctuating a bit. This test was successful in the fact that it provided me with enough information to be able to say with confidence that sand and water will not interfere with a metal detector.

In conclusion, the experiment showed me that metal detectors are a plausible tool to locate bombs in Swiss lakes as sand and water don’t affect its ability to detect metal. When just water or just sand was added, the metal detector reacted the same as without the water or sand. This is proven by the fact that the tin control test average was 12.5 cm and the test with sand and water was exactly the same distance. 

 

My hypothesis was incorrect because I thought the barriers, sand and water, would affect the electromagnetic wave’s ability to travel to the metal and back. The sand and water did not affect the metal detector. This test helps me in creating a design for a robot that can map the location of bombs on the bottom of a lake. By adding a metal detector to my robot, I will be able to find where bombs are present and where they are not.

The reason this happened, according to my research, was because the electromagnetic permeability of refined sand is very close to that of air. This is because it has very little magnetic material which would affect the electromagnetic waves.  Permeability is the amount of electromagnetic waves that can pass through a given material. This means that sand wouldn’t hinder electromagnetic fields. The sands at the bottom of lakes would have a much higher chance of containing magnetic material because of the bombs and other natural causes that my sand did not contain. Water’s electromagnetic permeability is 0.999 992 compared to air (1.000 000 37). Water's effect on the electromagnetic wave is so small that my metal detector didn’t pick it up. The electromagnetic permeability of sand and water are so close to air that it didn’t affect our metal detector. This is helpful so that I can understand why my experiment results were what they were and help us predict what will happen in the real world.

 

The data I collected in this experiment can help the world in many ways. This information will help me in designing a process to map out the bombs at the bottom of the lakes and could lead to a way to actually surface them safely. This information can help in other countries that have dumped bombs in water. Metal detectors can also be used for bomb detection above ground. If we used a metal detector over areas likely to have bombs, we may be able to reduce the risk of a bomb accidentally exploding. 

The project could also be used as a good basis for applying metal detectors in garbage clean up. A metal detector could be used to sort metal in a landfill so that we can reuse or dispose of the metal properly. Getting rid of the metal would reduce the volume in landfills and help us start cleaning up our planet. Similarly, it can also apply to garbage dumped in water. Other countries have dumped all sorts of waste including bombs in other bodies of water including the oceans. 

The information I discovered in my testing will help the real world because it will help protect us by identifying bombs in water. The fact that we can trust metal detectors’ reliability, even if there is something covering up the target, proves that it would be a good tool in these situations. If we can identify bombs we can get rid of ammunition before it accidentally explodes and causes incredible damage. Similarly, we can reduce damage to our environment by finding and disposing of metal waste in both landfills and bodies of water. 

Next Steps

With the information I received from these experiments I will be able to continue with the next steps of the project. The next thing I would want to do is build a prototype or model of the designs I plan. From there I could test and refine the robot. After that is done I could start thinking of ways to resurface the bombs in an environmentally safe way. I would need to research other ways to remove ammunition because I might be able to use something that has already been invented in my design.

 

• The metal samples might not have been pure. Instead of having a pure metal, which is pretty hard to get, they could have been two or three metals mixed together. This could have affected the results because if it wasn’t pure metal I can’t say this one type of metal can be easily found by a metal detector because it could have been multiple types of metal. But the part of the experiment was mostly to test the metal detectors capabilities, not the metals.
• The long piece of wood that held up the measuring tape moved a small amount during the Sand and Water Test. This could affect the results because the metal detector might not have been descending straight toward the metal. If I did this again I would more securely attach the dowel to the chairs or I could redesign it to be completely solid. 
• The metal detector might have picked up different metals than the samples and started beeping too soon. The chairs I used to test the metal detector had screws in them and the wall and floor around the test also had metal. If I redid it I could change the design so it was made entirely out of wood and plastic and I could perform the experiment outside to eliminate the metal in the house.
• The battery could have started to run low by the time I got to the final testing. However I started with a brand new battery with a voltage of 9.3v. If the battery had been running low the metal detector would have sent out a weaker electromagnetic field and so would have had to go closer to receive one, changing the results from what they would have been with a fully charged battery.
• As I was performing my experiment I learned that if the metal detector was turned on close to metal then it wouldn't work as well as if it had been turned on without metal close by. This could have affected my results because I didn't know this until I was halfway through the experiment resulting in inaccurate measurements. If this experiment was redone I would know about this fact in advance and be able to plan around it.

 

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I would like to thank my science fair teacher Ms.Burkell for providing me support while I was creating my project. She was a big help, providing amazing feedback and helping me figure out how to execute my dreams.

I would also like to thank my parents for helping and encouraging me along the way.

I would like to thank my incredible teachers for providing me time, space and energy for my project.