Worksheet: The Simple Magnifier

In this worksheet, we will practice defining the angular magnification of images produced by simple magnifiers and correlating this to their focal lengths.

Q1:

You view a mountain with a magnifying glass of focal length 𝑓=10 cm. What is the magnification?

  • A3.4x
  • B2.9x
  • C3.7x
  • D4.0x
  • E2.5x

Q2:

What will be the angular magnification of a convex lens with the focal length 2.5 cm?

  • A10x
  • B13x
  • C11x
  • D15x
  • E16x

Q3:

If the image formed on the retina subtends an angle of 30 and the object subtends an angle of 5.0, what is the magnification of the image?

  • A 5 . 6 𝑥
  • B 5 . 0 𝑥
  • C 6 . 0 𝑥
  • D 6 . 5 𝑥
  • E 6 . 9 𝑥

Q4:

How far should you hold a 2.1-cm-focal length magnifying glass from an object to obtain a magnification of 10x? Assume you place your eye 5.0 cm from the magnifying glass.

Q5:

A magnifying glass produces an angular magnification of 4.5x when used by a person with a near point of 18 cm. What is the maximum angular magnification obtained with the lens by a person with a near point of 45 cm?

  • A9.8x
  • B8.8x
  • C8.5x
  • D9.5x
  • E9.3x

Q6:

A magnifying glass forms an image 10 cm on the opposite side of the lens from the object, which is 10 cm away. What is the magnification of this lens for a person with a normal near point if their eye 12 cm from the object? The lens-to-retina distance is 2.00 cm.

  • A 1 . 6 x
  • B 2 . 9 x
  • C 2 . 5 x
  • D 2 . 1 x
  • E 3 . 3 x

Q7:

A doctor examines a mole with a 10.0 cm focal length magnifying glass, which is held 12 cm from the mole. What magnification does the lens produce?

Q8:

An object viewed with the naked eye subtends a 6.0 angle. If you view the object through a 10x magnifying glass, what angle is subtended by the image formed on your retina?

Q9:

A magnifying lens with a focal length of 14.0 cm is held 4.00 cm from an eye and the object is 13.0 cm from the eye. What is the magnification of the lens?

  • A8.33x
  • B12.3x
  • C9.25x
  • D10.7x
  • E7.00x

Q10:

Find the angular magnification of an image by a magnifying glass of 𝑓 = 6.3 cm if the object is placed 𝑑o = 5.8 cm from the lens and the lens is close to the eye.

Q11:

A magnifying glass produces a magnification of 4.00 when held at a distance of 6.00 cm from a coin. What is the focal length of the magnifying glass?

Q12:

What is the angular magnifier of a binocular that has a focal length of 1.9 cm for the eyepiece and a focal length of 9.0 cm for the objective?

Q13:

You view an object by holding a 3.50 cm focal length magnifying glass 10.0 cm away from it. How far from your eye should you hold the magnifying glass to obtain a magnification of 10.0x?

Q14:

While outdoors on a sunny day, a student holds a large convex lens of radius 5.0 cm vertically above a sheet of paper, producing a bright spot of light on the paper 2.0 cm in radius. The magnitude of the electric field within the bright spot of light is 𝐸 and that of the sunlight leaving the side of the lens facing the paper is 𝐸. Find the ratio of 𝐸 to 𝐸.

Q15:

The normal power for distant vision is 50.0 D. A young woman with normal distant vision can increase the power of her eyes by 13.0% by using accommodation. What is the power increase of her accommodated eyes?

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