# What does (simple) $j/cm^2$ represent AND how does this result $6.959j/cm^2$? [closed]

According to the image shown below, this specific Laser Hair Treatment device claims that it has a concentration of $6.959 j/cm^2$. So far by research I have found that it needs around $6\mbox{ to }7 J/cm^2$ for better hair growth. You can find a slight description of it here. However the specific product which has shown here also claims that it uses $443$ $J$ of energy per treatment which is 20 minutes long, and 80 Laser emitters with $678\pm 8$ nm of wavelength which covers an area of 582cm2 of the scalp out of $720cm^2$ of total scalp area. Here is the image of the Laser Hair Treatment Device which shows its specifications.

.

And here is the paragraph which they have mentioned its specifications and energy distribution.

The key to treating hair loss is lasers, but all lasers are not created equal. We use specially developed, high efficiency lasers that allow us to deliver the maximum amount of light and cover $582 cm^2$ of the $720 cm^2$ total scalp area in the average human head. We don't want to bore you with numbers, but with over $440$ Joules per treatment and an optimised wavelength of $678\pm 8$ nm, each of the $80$ lasers is precisely tailored for maximum hair growth.

According to my memory and knowledge I tried my best to get the result of $6.969 J/cm^2$ or something closer to it using these data and I failed. These are my questions.

1. What is (simple) $j/cm^2$ which is indicated here as $6.959 j/cm^2$? And why is it shown as $j/cm^2$ instead of $J/cm^2$?

2. Even so, how do I get the result of $6.959$ ($J/cm^2$ or $j/cm^2$) or something closer to it using these given data, as this device manufactures claim?

Thank you!

• This question appears to be off-topic because it belongs on Skeptics.SE Jan 17 '14 at 1:39
• Thank you for that suggestion @BrandonEnright. As you have said I have now re-posted the question at Skeptics.SE but I will still keep this question posted here for any further help from someone. Jan 17 '14 at 2:14
• IMPORTANT UPDATE: According to the new found facts after further research, we have found this video which is made by this device's manufacturers and if you go to 1 minute and 57 seconds of it, in the table which the person there explains, the 4th item shows that this device's concentration as $105 J/cm^2$ which puts the entire problem under confusion as the manufacturers have shown double standards of their product which if true will make this entire question invalid and useless. Jan 17 '14 at 3:01
• However I will still keep this posted here for anyone who could make a sensible explanation by any chance on these data and the result. Jan 17 '14 at 3:02

• Yes I'm starting to doubt it so as well. Because the first thing if it is really $J/cm^2$ what they have meant, it is a big mistake scientifically and even so like you've explained, it doesn't make sense how they have got $6.959 J/cm^2$ out of these data. Thank you for your answer. I would +1 your answer for sure but I lack the 15 reputation score to do so. Jan 17 '14 at 2:09