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Advice for Experiment with Budget

JDBruney

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Joined
Apr 8, 2021
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2
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Hi everyone,

First time posting to the site. Please tell me if there is a better thread to post this in.

So I need to pop a balloon underwater for an experiment. The acrylic tank has an angled mirror to redirect the laser beam to go through the bottom of the tank through a thin layer of water (2 cm or less) and then onto the surface of a submerged balloon. My questions are as follows:

-What wavelength do I need? (I have read that blue may be the best as it is absorbed less readily by water but maybe it is more expensive and unnecessary for such a thin layer)

-What power output is sufficient? (Google says 100mW)

-Optimum balloon color or type?

-What type of safety glasses should we purchase?

-Any accessories we will need? (Would like it to be mountable and to have either a wall adapter or rechargeable battery)

-What is the minimum cost laser you would recommend? (As long as it can pop the balloon from the above setup and is safe, that is all we need)

Thank you for any advice or insight.

-Dylan
 
Last edited:



CurtisOliver

Well-known member
LPF Site Supporter
Joined
Jun 12, 2015
Messages
7,259
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Welcome Dylan,
I'll answer each question in order.

You are correct that shorter visible wavelengths are least absorbed by water, you could however still use a red and not notice any major effects as water is generally transparent to visible wavelengths. The absorption is most noticed once you go into NIR to IR.

Power density is more important than power in this case, the higher the input power then naturally power density will increase. The best thing to do is to use a laser with good beam specs rather than just raw power. A 50mW 532nm will still pop balloons because of its smaller spot. 100mW is guaranteed to pop balloons. Balloons are also dependant on the amount of inflation. The more inflated they are, the more surface tension the balloon has to withhold. The laser is just weakening the surface of the balloon until the surface tension rips the balloon apart. The laser never even gets time to physically burn a hole in its surface.

Optimum balloon colour for visible lasers is black. Black absorbs the laser radiation the most therefore allows more energy to be absorbed and not reflected away.

Laser goggles will be dependant on what laser wavelength you have and what output power you are dealing with.
As it looks like you will be using either a blue or green laser. These are some of the best goggles out there and will cover you.
Use LPF445 for a member discount.

Accessories and setup is up to you.
 

RA_pierce

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Joined
Sep 16, 2007
Messages
3,566
Points
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Using a convex lens to focus the laser beam onto the surface you want to burn will increase power density.
An inexpensive 100-200 mW red laser module will do just fine for this. They can be found commonly on eBay in configurations that are mountable with wall adapted power supplies. These types of laser are often equipped with an adjustable collimating lens which will allow you to adjust the focal point without external optics.
 

JDBruney

New member
Joined
Apr 8, 2021
Messages
2
Points
1
Welcome Dylan,
I'll answer each question in order.

You are correct that shorter visible wavelengths are least absorbed by water, you could however still use a red and not notice any major effects as water is generally transparent to visible wavelengths. The absorption is most noticed once you go into NIR to IR.

Power density is more important than power in this case, the higher the input power then naturally power density will increase. The best thing to do is to use a laser with good beam specs rather than just raw power. A 50mW 532nm will still pop balloons because of its smaller spot. 100mW is guaranteed to pop balloons. Balloons are also dependant on the amount of inflation. The more inflated they are, the more surface tension the balloon has to withhold. The laser is just weakening the surface of the balloon until the surface tension rips the balloon apart. The laser never even gets time to physically burn a hole in its surface.

Optimum balloon colour for visible lasers is black. Black absorbs the laser radiation the most therefore allows more energy to be absorbed and not reflected away.

Laser goggles will be dependant on what laser wavelength you have and what output power you are dealing with.
As it looks like you will be using either a blue or green laser. These are some of the best goggles out there and will cover you.

Use LPF445 for a member discount.

Accessories and setup is up to you.


Thank you for you insight! I think I found a REALLY cheap laser that fits the bill (took a hint from RA_Pierce). Does this look like a scam to you/ does anything looks misleading? I couldn't post the link, so I attached a screenshot of the page (I had to make some grainer then others to upload):
 

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Eseyria

New member
Joined
May 11, 2021
Messages
15
Points
1
Hi everyone,

First time posting to the site. Please tell me if there is a better thread to post this in.

So I need to pop a balloon underwater for an experiment. The acrylic tank has an angled mirror to redirect the laser beam to go through the bottom of the tank through a thin layer of water (2 cm or less) and then onto the surface of a submerged balloon. My questions are as follows:

-What wavelength do I need? (I have read that blue may be the best as it is absorbed less readily by water but maybe it is more expensive and unnecessary for such a thin layer)

-What power output is sufficient? (Google says 100mW)

-Optimum balloon color or type?

-What type of safety glasses should we purchase?

-Any accessories we will need? (Would like it to be mountable and to have either a wall adapter or rechargeable battery)

-What is the minimum cost laser you would recommend? (As long as it can pop the balloon from the above setup and is safe, that is all we need)

Thank you for any advice or insight.

-Dylan
That is exactly what I was looking for, thanks!
 

farbe2

Active member
Joined
Oct 3, 2018
Messages
115
Points
43
Did you think about using a different method? Wire with a resistor attached to the ballon would work to.
The laser might have a problem to pop the balloon on long distances.
 




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