Problem

A telescope is constructed from two lenses with f…

01:56

Problem 59 Hard Difficulty

. A person with a near point of $85 \mathrm{cm},$ but excellent distant vision, normally wears corrective glasses. But he loses them while traveling. Fortunately, he has his old pair as a spare.
(a) If the lenses of the old pair have a power of $+2.25$ diopters, what is his near point (measured from his eye) when he is wearing the old glasses if they rest 2.0 $\mathrm{cm}$ in front of his eye?
(b) What would his hear point be if his old glasses were contact lenses instead?

Answer

a. 30.9 $\mathrm{cm}$
b. 29.2 $\mathrm{cm}$

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Video Transcript

simple question. One he was asking us, Um, look, what is his near points when he's wearing glasses? Okay, so we know the power of old glasses is two points. Who fired the orbiter's? Okay, So, actually, when you find out it off, just distance first, You know, if you all the distance off his near points when he started wearing the glasses. Well, first we know that the power is you go to possibly to a point to A by doctors. Okay, Which is equal to when were ash. Okay, so one over Focal lens is equal deposit. Still going to buy the openers? If you don't sound, uh, calculation, you'll get the focal lens is equal to zero point for 44 meter, which is 44.4 sending you here. Okay, so now we know that you was an object. This and chemical too. We have over b minus that. And we know that the these case, its secret connective 85 sending me here minus two centimeter. Okay, so the near point phone glasses is 85 70 reminds two centimeter. It was 83 centimeters. And the next time before the presence is before the President Perrin. This is just means that the image is inverted. Okay, so this will give us me is equal to connective. 83 centimeter. Okay, so now we can start calculating the object. This which is you equal to? Um, we have we just next 83 seven year times 44 point for sending me here over Conectiv, 83 centimeters minus 44. Going forward centimeter. And this would give us the object. Distance is equal to Conectiv are receding is actually passive. Sorry is positive. Sorry. It was positive. 20 A When I sending year. Okay, so the near points when he's wearing glasses, they say l you sing with you Plus two centimeter because remember, the old glasses is two points Oh, centimeters in front of his eyes. So when you add it to some years back and we get 28.9 sending here plus 27 year, which is 30.9. Save me. Okay, so the near point of the person when I is 30 point nights and year, Okay. So still caring question to So Question two was asking us what will happen if the old glasses was replaced by a contact lenses. So he wants to play. We place buying the contact lenses. Then he's the near point B, which is the image Business will be disconnected. Any five centimeter sees the contact lenses on your eyeball soldiers. Basically, there's no distance between your confidence to your eyeball. So just the near point given following the question was negative. 85 centimeter. Okay. And naked sign here. It just means the images thing. Bird. Okay, we know you. I'm sorry. The focal lens on a previous question was 44 24 centimeters. And we know we still need to figure out E opta distant police case. Okay, which is it was We have over B minus that. And we got 85 centimeter times 44 point for seven years over negative. 85 7 years minus. What do you for pointing forward seven meters, which would give us a value. Ah, about 29.2 centimeters. So I told them 0.2 centimeters will be the near point for this case because we don't really do that. That's what it does. Any reader back because the distance between the continents to your eyeball is basically basically zero. Okay, So 29.2 centimeter is the answer for passion. So these are the solutions. Full question. Thank you.

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