Absorbance =

100÷%T
A=

2.105 <=>
<=> A=0.3233
To 47.5%T corresponds 0.3233 absorbance.
You could say something along the lines of:
"Hey, Friend, what's so good about weed? Why are you always smoking it?"
If he's smoking it for medical purposes, then just drop it, but if it's illegal and he's doing it to "look cool", then I would further ask questions about it.
The glycemic index predicts the way certain foods affect blood sugar levels.
Excluding themselves from an activity they normally love
Drug addiction is a chronic disease characterized by compulsive, or uncontrollable, drug seeking and use despite harmful consequences and changes in the brain, which can be long lasting. These changes in the brain can lead to the harmful behaviors seen in people who use drugs. Drug addiction is also a relapsing disease. Relapse is the return to drug use after an attempt to stop.