Exam 19: Optical Instruments

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

A nearsighted person has a far point that is 4.2 m from his eyes. What focal length lenses must he use in his contact lenses to allow him to focus on very distant mountains?

A compound microscope has a 18-cm-long barrel and an objective lens with a focal length of 8.0 mm. What is the focal length of the eyepiece to give a total magnification of 240? It is adjusted for minimum eyestrain for persons 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 microorganism with magnification M_M, with what magnification does Jack see it?

To maximize the magnification of a refracting telescope, what lenses should you choose?

A simple refracting telescope provides large magnification by employing

What type of lens is used to make a magnifying glass?

A student constructs an astronomical telescope and wishes it to have a magnification of 10. If the telescope has an objective lens of focal length 0.50 m, what must be the focal length of the eyepiece?

For an eye that is 2.4 cm in diameter, what must be the range of focal lengths of the lens to focus objects from the near point (25 cm) to infinity on the retina?

A farsighted girl has a near point at 2.0 m but has forgotten her glasses at home. The girl borrows eyeglasses that have a power of +2.75 diopters. With these eyeglasses, what is the near point of the girl, assuming that she wears them extremely close to her eyes?

A farsighted person cannot see clearly objects that are closer to her eyes than 60.0 cm. Which one of the following combinations represents the correct focal length and the refractive power of the contact lenses that will enable her to comfortably see the objects at a distance of 25.0 cm from her eyes?

A nearsighted person has a far point of 50 cm for his right eye and 150 cm for his left eye. For each eye, what power contact lens will allow the person to see gorgeous sunsets?

A nearsighted person wears contact lenses having a power of -0.15 diopters. What is the person's uncorrected far point?

The length of a telescope is 1.60 m and it has a magnification of 60.0. What is the focal length of the eyepiece?

If the diameter of a radar dish is doubled, what happens to its resolving power assuming that all other factors remain unchanged?

The distance between the object to be viewed and the eyepiece of a compound microscope is 25.0 cm. The focal length of its objective lens is 0.200 cm and the eyepiece has a focal length of 2.60 cm. What is the magnitude of the total magnification of the microscope when used by the person of normal eyesight if it is designed for minimum eyestrain?

A nearsighted person cannot see objects beyond 80 cm from his eyes. Which one of the following combinations represents the correct focal length and the refractive power of the contact lenses that will enable him to comfortably see the distant objects clearly?