Cuesta College, San Luis Obispo, CA
NASA Goddard Space Flight Center
asd.gsfc.nasa.gov/bettii/
The two far-infrared reflector telescopes of the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII)[*] have the same 0.50 m (1.6 ft) diameter, and are separated by a distance of 8.0 m (26 ft) between them. This telescope system is attached to a balloon that ascends to an altitude of 40 km (25 miles) in the upper atmosphere.[**] Taking this far-infrared telescope system into the upper atmosphere improves the light-gathering power due to less __________ at high altitudes.
(A) absorption.
(B) turbulence.
(C) light pollution.
(D) temperature fluctuations.
[*] S. A. Rinehart ; R. B. Barclay ; R. K. Barry ; D. J. Benford ; P. C. Calhoun, et al., "Design and status of the Balloon Experimental Twin Telescope for infrared interferometry (BETTII): an interferometer at the edge of space," Proc. SPIE 8445, Optical and Infrared Interferometry III, 844508 (September 12, 2012), dx.doi.org/10.1117/12.926376.
[**] asd.gsfc.nasa.gov/bettii/.
Correct answer (highlight to unhide): (A)
Far-infrared light entering the top of the atmosphere from space does not make it down to sea level (the bottom edge of the graph), due to absorption of this wavelength by the atmosphere. However, it can still be detected in the upper atmosphere, as has traveled a shorter distance through the atmosphere, where there was less absorption (primarily due to water vapor).
Section 70158
Exam code: quiz03St3M
(A) : 3 students
(B) : 11 students
(C) : 17 students
(D) : 1 student
Success level: 15% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25
Section 70160
Exam code: quiz03Nz6L
(A) : 0 students
(B) : 8 students
(C) : 12 students
(D) : 2 students
Success level: 5% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0
Comment from student 7890:
ReplyDeleteI think the question could have been worded more clearly:
"Due to there being less ________ at lower altitudes, this far-infrared telescope system is taken to the upper atmosphere to improve its light-gathering power."