While this may seems like a strange question, I'll try to explain it the best I can. Like 75% of Americans, I wear glasses and contacts to correct my worsening vision. I'm not far sighted so objects in the distance appear blurry. I took my glasses off to look at my iPad. After doing so I noticed in the reflection of the glass, my lamp. The lamp is in the distance and looks blurry to me. But on my iPad's glass it was blurry unlike the rest of the objects on screen, including the glass which I could see clearly because I'm near-sighted. It is strange to me why the reflection was blurry even though it was close up. How can this be?
Answer
This is simply the law of reflexion: if you trace a ray diagram for objects reflecting in your iPad screen, you are looking at light from a virtual image that is as far beyond your screen as the real source of light is from the iPad screen. So if the lamp is, say, 3 metres behind your shoulder, when you look at the iPad screen the reflected light is exactly like that from a lamp 3 metres beyond you iPad screen ahead of you. Put simply, you are looking at light diverging from a distant source, not from the iPad screen, so it will look blurry to you if a lamp that is really 3 metres beyond your iPad screen is blurry.
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