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Blurry Mirror on the Wall

Your Smartness:

I'm nearsighted, and when I look in the mirror without my glasses, I can see myself okay but things across the room look blurry. But if the mirror is close enough for me to see my own reflection clearly, then why can't I see the reflection of things across the room? I'm seeing both reflections from the same distance. I'm sure you can clear things up.

-- Four Eyes, El Cajon

Yeah, I can. But you're not going to believe me anyway. Nobody ever seems to buy this story, so here goes nothing.

We see objects by focusing the light that bounces off them and travels to our eyes. To say you're nearsighted means your eyes can't focus light that travels farther than a certain short distance.

When you look at a reflection in a mirror, and the object is eight feet from the mirror and you're, say, two feet away, you're not seeing light coming from just two feet away. You're seeing light that has traveled from the object to the mirror, has reflected from the surface of the mirror, and then traveled another two feet to your eyes. If your eyes can't focus light that's traveled ten feet, they won't be able to focus light that has traveled eight feet to the mirror and two feet more to your eyes. In terms of distance, the image in your mirror is an exact duplicate of the reality it is reflecting.

Ever wonder how an eye doctor can test your distance vision in his tiny examining room? He puts the eye chart behind you, then projects the chart onto a mirror across the room. That mirror reflects the chart onto a mirror behind you, and so on. The light zigzags back and forth among a series of mirrors, and the final reflection is directed toward your eyes. By the time you see it, the light from the chart has traveled several times the length of the room. Otherwise, he would have to give you an eye test in a bowling alley.

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Your Smartness:

I'm nearsighted, and when I look in the mirror without my glasses, I can see myself okay but things across the room look blurry. But if the mirror is close enough for me to see my own reflection clearly, then why can't I see the reflection of things across the room? I'm seeing both reflections from the same distance. I'm sure you can clear things up.

-- Four Eyes, El Cajon

Yeah, I can. But you're not going to believe me anyway. Nobody ever seems to buy this story, so here goes nothing.

We see objects by focusing the light that bounces off them and travels to our eyes. To say you're nearsighted means your eyes can't focus light that travels farther than a certain short distance.

When you look at a reflection in a mirror, and the object is eight feet from the mirror and you're, say, two feet away, you're not seeing light coming from just two feet away. You're seeing light that has traveled from the object to the mirror, has reflected from the surface of the mirror, and then traveled another two feet to your eyes. If your eyes can't focus light that's traveled ten feet, they won't be able to focus light that has traveled eight feet to the mirror and two feet more to your eyes. In terms of distance, the image in your mirror is an exact duplicate of the reality it is reflecting.

Ever wonder how an eye doctor can test your distance vision in his tiny examining room? He puts the eye chart behind you, then projects the chart onto a mirror across the room. That mirror reflects the chart onto a mirror behind you, and so on. The light zigzags back and forth among a series of mirrors, and the final reflection is directed toward your eyes. By the time you see it, the light from the chart has traveled several times the length of the room. Otherwise, he would have to give you an eye test in a bowling alley.

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4S Ranch Allied Gardens Alpine Baja Balboa Park Bankers Hill Barrio Logan Bay Ho Bay Park Black Mountain Ranch Blossom Valley Bonita Bonsall Borrego Springs Boulevard Campo Cardiff-by-the-Sea Carlsbad Carmel Mountain Carmel Valley Chollas View Chula Vista City College City Heights Clairemont College Area Coronado CSU San Marcos Cuyamaca College Del Cerro Del Mar Descanso Downtown San Diego Eastlake East Village El Cajon Emerald Hills Encanto Encinitas Escondido Fallbrook Fletcher Hills Golden Hill Grant Hill Grantville Grossmont College Guatay Harbor Island Hillcrest Imperial Beach Imperial Valley Jacumba Jamacha-Lomita Jamul Julian Kearny Mesa Kensington La Jolla Lakeside La Mesa Lemon Grove Leucadia Liberty Station Lincoln Acres Lincoln Park Linda Vista Little Italy Logan Heights Mesa College Midway District MiraCosta College Miramar Miramar College Mira Mesa Mission Beach Mission Hills Mission Valley Mountain View Mount Hope Mount Laguna National City Nestor Normal Heights North Park Oak Park Ocean Beach Oceanside Old Town Otay Mesa Pacific Beach Pala Palomar College Palomar Mountain Paradise Hills Pauma Valley Pine Valley Point Loma Point Loma Nazarene Potrero Poway Rainbow Ramona Rancho Bernardo Rancho Penasquitos Rancho San Diego Rancho Santa Fe Rolando San Carlos San Marcos San Onofre Santa Ysabel Santee San Ysidro Scripps Ranch SDSU Serra Mesa Shelltown Shelter Island Sherman Heights Skyline Solana Beach Sorrento Valley Southcrest South Park Southwestern College Spring Valley Stockton Talmadge Temecula Tierrasanta Tijuana UCSD University City University Heights USD Valencia Park Valley Center Vista Warner Springs
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