Compound Microscope: 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.
A. 1.3 m
B. 1.5 cm
C. 1.9 cm
D. 2.1 cm
E. 2.3 cm
Answer: D
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In an x-ray diffraction experiment, using x-rays of wavelength ? = 0.434 × 10^?10 m, a first-order maximum occurred at 8° off the crystal plane. Find the distance d between crystal planes
a. 1.56E–10 m b. 2.19E–11 m c. 4.88E–10 m d. 1.70E–9 m e. 3.12E–10 m
The brightest object in the sky is
a. the Sun. b. the Moon. c. Venus. d. Mars.
What is the symbol used on the periodic table for the element Rubidium?
a. Rf b. Hs c. Rb d. No e. U