Advice for a newcomer

[cdog]

Hello,
I'm looking for some advice on my first laser purchase. I need a laser to help with physics demonstrations (refraction and that sort of thing) in daylight, and so by the sounds of it I need something about 5mW.

I've been reading loads of posts and advice over the last few days, and I know way more than I did before, and know I want to choose a specific product.



First of all, on my student budget, I can't really afford anything more than about 30 USD. Is this a realistic budget to get a decent 5mW laser?

Does the colour really matter? What colour beam will show up best going through a glass block and water tank?

Since I'm only getting a 5mW laser, protective glasses aren't necessary, right?

Since the advertised power output and the real power of cheap lasers are often quite different, and I can't afford to buy a $50 LPM, are there any tests I can do to see if its reflections are dangerous? I'll be doing the demonstrations with children, and I can't afford to buy safety glasses for all of them, so I want to keep things safe. Obviously I'll handle it very carefully, and not let the children play with it.

I've had a looked at the recommended online shops, but since I live in Europe, the shipping costs totally screw up my budget.

I've included a few links of lasers I've found, and they seems suspiciously cheap, but the ratings of the sellers are good, so I'm tempted to go for it. I would appreciate any advice.

https://www.dx.com/p/5mw-532nm-green-laser-pointer-pen-with-dx-logo-2-aaa-2008323#.XQ4GW2wzY5k
https://www.ebay.nl/itm/High-Power-...233008?hash=item2f09f0b5b0:g:zVUAAOSws8Rc~LkW
https://www.ebay.nl/itm/High-Power-...233207?hash=item2f09f0b677:g:6ykAAOSwOPxdB6LW

Thank you very much for your time.

 

[GSS]

Just a quick post. I believe none of these laser will be 5mw, at least the 532 green lasers.
They are rated at 5mw for custom's reasons. The might run at 30mw to 80mw. Believe it or not it's harder and more expensive to make a one at a low powers like 5mw to 30mw.
Not sure about deal extreme but again I also believe they were banned from selling lasers to the US?? I know your not in the US but the reason they were banned was because they got flagged for selling laser rated at 5mw that were much higher..
Let some others chime in...

 

[cdog]

Thanks a million for the information GSS. Is there an easy way to determine if a laser is dangerously above 5mW? Like if it can burn paper, it must be x mW...

 

[GSS]

Everyone will say only a LPM but some little things might give an idea.
Assume first a 532 green won't be less than 35 to 40mw..
If it pops a black balloon it will be maby at least 60mw..
If it won't go through a thin black plastic shopping bag with the laser basicly touching the bag then that's weakest and maby no more than 35mw??
Your best bet is to get a legit built pointer and not risk it.
"Optotronic's" builds a true 4.99mw and I think "Z bolt" does but they cost probably $20 without shipping.

 

[Lifetime17]

Hi .
Yes Yes the 532 green would be perfect for what your intentions are. GSS hit the nail straight on go with the 532 its a bright beautiful green beam and the are cheap . you might want to by a 450,or 455nm blue also just for the hell of it then you can experiment with two different WL's and save some cash to .

Rich

 

[paul1598419]

If you insist on a 5 mW laser for your purposes, you won't be able to remain in your budget. Also, if you are planning on having a visible beam going through a prism and a tank of water, that likely won't be possible in a lit room. You would need fog and to haze your water to be able to see the beam in a lit room. If you set it up properly, you can get by with a higher power laser as long as you make certain that any reflections don't come near anyone. In this case you could use a 301 or 303 532nm green laser pointer from eBay which you can buy for under $12.00 with cheap batteries and charger.

 

[Lifetime17]

Hi, The first three links you posted are fine for what you need to do. And for that price you get three pens in different WL's.
Rich

 

[cdog]

Thanks for all of your advice
I looked at GSS' suggestion of Optotronic and ZBolt, but their 5mW lasers were close to $100 with shipping, and that's not really feasible for me at the moment, so I'm thinking of going for the pack of 3 on ebay that I posted (https://www.ebay.nl/itm/High-Power-...233207?hash=item2f09f0b677:g:6ykAAOSwOPxdB6LW), and buy a handful of these safety glasses, https://www.amazon.com/gp/product/B003OBZ64M/ref=oh_o00_s02_i01_details?th=1

I'm thinking to keep things safe, I'll just attach it to a tripod stand so as to not let it move about and accidentally reflect off things. Although since I want to show refraction through glass and water, this will be tricky, as it'll be firing into an aquarium tank.

I'd appreciate any comments on my decision so far, and any other ideas on how to increase the safety of my plan. I won't be able to afford to buy enough safety glasses for everyone, so I'm thinking I'll just use the glasses when I'm designing the experiment and setting things up before the demonstration.
Thanks again for all of your suggestions

 

[Lifetime17]

Hi,
Great choice more WL's and bang for your buck smart choices , Remember to post a thread upon your completion that would be great .

Rich

 

[cdog]

I've just been reading other pages, and someone mentioned that some kind people on this site will use the LPM on people's lasers if they pay for the shipping costs.
I've been looking, but I haven't been able to find a thread where people offer this. Could you please link the thread if it exists? It'd be awesome if one of these people live in Ireland

 

[Lifetime17]

Hi, I would LPM those lasers ,but unfortunately I reside in the states. I would do it for free the only cost to you would be shipping. Then there's another issue with customs. Wish I could have helped.

Rich

 

[GSS]

There is a LPM owners thread somewhere with members offering to measure other members lasers. I'm sure someone might be at least in your Country..
Those Uvex glasses are not laser safety glasses but more eye protection glasses that "happen" to block blue lasers but not sure about the other WL's..
The other option is the cheap generic ones. I have won them for a $1.25 at auction. So buying 5 pairs for example could be possible.. They charge more usually when they come with a holding case, so you can do without the cases and bid..
Just remember they are in the "better than nothing" catagory. Testing the side lenses first will give you a good idea how well they work.

 

[Encap]

EU restricts laser pointers to 1mW and using higher output lasers around children and with no eye protection does not sound like a good idea because you can not demonstrate any effort at safety or legal limit considerations with a 5mW much less a cheap Chinese 50mW - 100mW sold as 5 mW to circumvent Country law, rules, and regulation of laser sales
See: https://www.laserpointersafety.com/...s/e1013789277f666eee69b4d4a7b4bfb7-383.php#on

There are a lot of way to demonstrate refraction without a laser see: https://www.scientificamerican.com/article/now-you-see-it-testing-out-light-refraction/

 

[paul1598419]

Those cheap pointers at three, 650nm, 532nm and 405nm, for $8.99 are not going to be your best options. The green one is a diode pumped solid state laser and will tend to mode hop because it has little heat sinking. The 405nm one is nearly invisible because it is so close to UV and the 650nm one is not very bright either, though it is more visible than 405nm. If I were you, I would try for a 532nm green laser as a 303 type on eBay. They are ~$6.00 unless you buy them with the cheap batteries and charger.

 

[Anthony P]

Just a thought... adding some contaminants to your tank will make the beam highly visible. Sorry, don't remember the recipe.

 

[Coonie]

Salt would make it murky. Heck even just dirt from outside would do it as long as you stir it around first