9. an object 20 cm to the left of a convex lens is 1.0 m in height. What is the

Question

9. an object 20 cm to the left of a convex lens is 1.0 m in height. What is the height
and location of its image if the lens has a magnification of -2.0?___m and
______cm on the left/right side of the lens?


10. Imagine you are nearsighted (can only see close objects clearly and far objects are blurry). At your last eye doctors appt, your optometrist tells you that she will neeed to increase your prescription because as it turns out light is focusing "too soon" or in front of your retina. You respond, "obviously, I will need a converging/diverging lens with a higher/lower focal distance?

Explanation / Answer

Given: distance of the object from the lens u = 20 cm magnification of the lens m = -2.0 magnification of the lens m = -v/u   .......   (1) here v is the object distance v = mu    = (-2.0)(20cm)    = -40 cm when the image formed by a spherical lens is real, it is alos inverted w.r.t object and is on the same side of the lens as the object. since both v and u are negative . so image is also left of the lens. (b) This defect of eye is called short sightedness or Myopia. To correct short-sightedness vision , a diverging lens (concave) of suitable focal length is used. Focal length of the lens for a short-sighted person is equal to the negative value of the person's far point.

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