Worksheet: Microscopes

In this worksheet, we will practice calculating the separations between lenses used in microscopes, their powers and focal lengths, and the magnifications produced by them.


A 0.150 cm-focal length microscope objective is 0.155 cm from the object being viewed.

What magnification is produced?

  • A 2 7 . 5 x
  • B 2 5 . 0 x
  • C 3 3 . 3 x
  • D 3 0 . 0 x
  • E 3 5 . 0 x

What is the overall magnification if an 8x eyepiece (one that produces an angular magnification of 8.00) is used?

  • A 2 4 0 x
  • B 2 8 0 x
  • C 2 5 0 x
  • D 2 3 0 x
  • E 3 0 0 x


The objective and the eyepiece of a microscope have the focal lengths 3.0 cm and 10 cm respectively. Find the distance between the objective and the eyepiece that will result in a 10x magnification by the microscope.


An amoeba is 0.305 cm away from the 0.300 cm-focal length objective lens of a microscope, as shown.

How far behind the objective lens is the image formed by the objective lens?

What is the magnification of the image formed by the objective lens?

  • A−60.0x
  • B−62.3x
  • C−58.0x
  • D−55.5x
  • E−64.0x

An eyepiece with a 2.00-cm focal length is placed 20.0 cm from the objective. How far in front of the eyepiece is the final image?

What angular magnification is produced by the eyepiece?

What is the overall magnification produced by combining the objective lens with the eyepiece?

  • A−850x
  • B−820x
  • C−800x
  • D−810x
  • E−880x


A microscope can accept light from objects at angles as large as 𝛼 = 6 5 . The microscope is used to observe structures that can be resolved when illuminated with light of wavelength 450 nm.

What is the size of the smallest structure that can be observed using the microscope in air?

What is the size of the smallest structure that can be observed using the microscope if the structure is immersed in oil, with an index of refraction of 1.50?


Find the minimum separation of two objects viewed through a microscope that are placed very close to the focal point of the objective lens. Use a value of 450 nm for the light from the object, a value of 4.00 cm for the focal length of the lens, and a value of 5.00 cm for the diameter of the microscope’s objective lens.

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