Exam 27: Optical Instruments

The focal lengths of the objective and eyepiece in a compound microscope are 0.50 cm and 2.00 cm, respectively. An object is placed at a distance of 0.52 cm from the objective. If the final image seen by the eye is at a distance of 25 cm from it, what is the magnification?

What is the focal length of a pair of contact lenses that will allow a person with a near point of 125.0 cm to read a newspaper held 25.0 cm from his eyes?

What power contact lens must be used to correct the vision of a nearsighted person whose far point is 40 cm?

Farsightedness can usually be corrected with

A very fine sample is placed 0.15 cm from the objective of a microscope. The focal length of the objective is 0.14 cm and of the eyepiece is 1.0 cm. The near-point distance of the person using the microscope is 25.0 cm. What is the final magnification of the microscope?

What is the focal length of the combined lenses with individual powers of 8.0 diopters and 4.0 diopters?

A magnifying glass of focal length 150. mm is used to examine an old manuscript. (a) What is the maximum magnification given by the lens? (b) What is the magnification for relaxed eye-viewing (image at infinity)?

A person with normal eyesight uses a converging lens of focal length 10 cm. He holds the lens close to his eye to finish an engraving job. At what distance from the job he must hold the lens?

What is the power of the lens that has a focal length of 40 cm?

You have a choice between two lenses of focal lengths f_a and f_b = 2 f_a to use as objective lens in building a compound microscope. If the magnification you obtain using lens A is M_a, what will be the magnification when using lens B?

The focal length of a converging lens is 10 cm. What is the magnification of this lens if the image is viewed by a relaxed eye with a near point of 25 cm?

Jack and Mary view the same microorganism through the same compound microscope. Mary's near point distance, N_M, is twice as large as Jack's near point distance, N_J. If Mary sees the micro-organism with magnification M_M, the magnification with which Jack sees it is

A refracting telescope has an eyepiece of focal length -80. mm and an objective of focal length 36. cm. What is the magnification?

The focal lengths of the objective and the eyepiece of a microscope are 0.5 cm and 2.0 cm, respectively, and their separation adjusted for minimum eyestrain is 6.0 cm. The near-point distance of the person using the microscope is 25.0 cm. If the microscope is focused on a small object, what is its final magnification?

The process of changing the shape of the lens, and hence adjusting its focal length, is referred as accommodation.

A person can read the newspaper when it is held at 60 cm from his eyes. What should the focal length of his contact lenses be to allow him to read the newspaper comfortably at a distance of 30 cm?

The refractive power of a lens used as a magnifying glass is negative.

The focal lengths of the objective and the eyepiece in a microscope are 0.29 cm and 2.5 cm, respectively. An object is placed 0.3 cm from the objective. The image of this object is viewed with the eyepiece adjusted for minimum eyestrain. What is the distance between the objective and the eyepiece?

The near point of a normal human eye is infinity.

John is nearsighted and cannot see things beyond 90 cm from his eyes. What is the refractive power of the contact lenses that will enable him to see distant objects clearly?