Is it the LCD screen or back light?

My son left his iPad in the rain. I let it dry out for a week and put it in dry rice to dry it out (the first 2 days). At first I got no response from turning it on. After charging it over night, I got the charging noise (I unplugged and plugged it in to get that noise). After a few more hours of charging, I got the noise when I turned it on and also a "screen shot" noise. We noticed then, at night with artificial room lighting, "ghost" shadows of the icons. We are able to turn on iTunes and a movie we had downloaded. The sound worked on both of those. The iPad appears to be working, but we are now trying to figure out if it's the LCD screen that is shot or just the back lighting, since we can barely make out the icons in the right light.