When a person with a near point at 28 cm uses a certain magnifying glass, it pro

Question

When a person with a near point at 28 cm uses a certain magnifying glass, it produces an angular magnification of 7.0 with the image very distant. What is the focal length of the lens of this magnifying glass? 2.0 cm 3.0 cm 4.0 cm 5.0 cm 6.0 cm A lens of focal length 40 mm is used as a magnifier. The object being viewed is 5 J mm long, and is positioned at the focal point of the lens. The user of the magnifier has a near point at 25 cm. What is the angular magnification of the magnifier? A microscope has an objective lens of focal length 1.40 mm and an eyepiece of focal length 20.00 mm. It is adjusted for minimum eyestrain for persons with a near point of 25.0 cm. A blood sample is placed 1.50 mm from the objective, flow far apart are the lenses?

Explanation / Answer

10)   focal length of lens = 28/(angular magnification)

                                         = 28/7   =   4 cm

=> option C) is correct .

12) angular magnification , M =   -fo/fe

Also, 1/v + 1/u = 1/f

=> Far apart are lens = 20 mm

=> option A) is correct .

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