Exam 19: Optical Instruments

You have available lenses of focal lengths 2.0 cm, 4.0 cm, 8.0 cm, and 16.0 cm. If you could use any two of these lenses to build a telescope, what is the maximum magnification you could achieve for comfortable viewing of a planet?

Mary builds a simple refracting telescope using two lenses of focal length 80 cm and 5.0 cm. The respective diameters are 60 mm and 10 mm. How many degrees wide does the moon appear through the telescope if it appears only 1/2 degree wide with the "naked eye"?

A student constructs an astronomical telescope with a magnification of 10. If the telescope has an objective lens of focal length 0.50 m, what is the resulting length of the telescope?

A lens of focal length 40 mm is used as a magnifier. The object being viewed is 5.3 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?

Cal is viewing the Moon with his new telescope, using a 10-mm focal length eyepiece. For greater detail, he wishes to double the magnification of his telescope. An eyepiece having which one of the following characteristics will accomplish this for him?

Given perfect lenses, what is the main reason that a telescope with a large-diameter objective lens can produce a sharper image than one with a small-diameter lens?

A person is nearsighted with a far point of 75.0 cm. (a) What focal length contact lens is needed to give him normal vision? (b) What is the power of the corrective lens?

The focal lengths of the objective lens and the eyepiece of a microscope are 0.50 cm and 2.0 cm, respectively, and their separation is 6.0 cm when adjusted for minimum eyestrain for a person with a near point of 25.0 cm. If the microscope is focused on a small object, the magnitude of its final overall magnification is closest to

The angular magnification of a refracting telescope is 40. When the object and final image are both at infinity, the distance between the eyepiece and the objective is 143.5 cm. The telescope is used to view a distant radio tower. The real image of the tower, formed by the objective, is 6.0 mm in height. The focal point of the eyepiece is positioned at the real image. What is the angle subtended by the final image of the tower?

The focal length of the lens of a simple film camera is 40.0 mm. By what amount should the distance between the lens and the film be increased or decreased to change the focus from a person who is 25 m from the lens to one who is 4.0 m from the lens?

Nearsightedness is usually corrected with

The near point of a farsighted person is 100 cm. She places reading glasses very close to her eyes, and with them she can comfortably read a book at a distance of 25 cm. What is the power of the lenses in her reading glasses?

What is the focal length of the corrective contact lens needed by a nearsighted person whose far point is at 60 cm?

The distance between the object to be viewed and the eyepiece of a compound microscope is 18.0 cm. The focal length of its objective lens is 0.80 cm and the eyepiece has a focal length of 2.3 cm. The near-point distance of the person using the microscope is 25.0 cm. What is the magnitude of the total magnification of the microscope if it is designed for minimum eyestrain?

Treat the pupil of your eye as a circular aperture of diameter 3.5 mm. Light of wavelength 500 nm is used to view two point sources that are 283 m distant from you. How far apart must these two point sources be if they are to be just barely resolved by your eye, assuming that the resolution is limited by diffraction?

For relaxed viewing with a microscope or a telescope, the eyepiece is adjusted to place the image at

The focal length of the objective lens of a telescope is 75.0 cm, and the eyepiece has a focal length of 6.00 cm. What is the magnification of this telescope?

The objective and the eyepiece of a refracting astronomical telescope have focal lengths of 320 cm and 4.0 cm, respectively. The telescope is used to view Neptune and the final image is set at infinity. The diameter of Neptune is 4.96 × 10⁷ m, and its distance from Earth at the time of observation is 4.4 × 10¹² m. What is the angle (in milliradians) subtended by the final telescopic image of Neptune?

Which one of the following is a characteristic of a compound microscope?

The focal length of a magnifying glass is 15 cm. If the near point of a person is 25 cm, what is the angular magnification of the glass for this person when his eyes are focused at infinity?