“2016年IOAA理论第8题-U波段测光”的版本间的差异
（创建页面，内容为“==英文题目== '''(T8) U-Band photometry''' A star has an apparent magnitude 𝑚<sub>U</sub> = 15.0 in the U-band. The U-band filter is ideal, i.e., it has perfe…”） |
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𝑓 = 3631 × 10<sup>−0.4𝑚</sup>Jy | 𝑓 = 3631 × 10<sup>−0.4𝑚</sup>Jy | ||
| − | (T8.1) Approximately how many U-band photons, | + | (T8.1) Approximately how many U-band photons, 𝑁<sub>0</sub> |
, from this star will be incident normally on a | , from this star will be incident normally on a | ||
1 m<sup>2</sup> | 1 m<sup>2</sup> | ||
| 第25行： | 第25行： | ||
(T8.2) What is the ratio, 𝑅, of number of photons received per second from the star to that received | (T8.2) What is the ratio, 𝑅, of number of photons received per second from the star to that received | ||
from the sky, when measured over a circular aperture of diameter 2′′? | from the sky, when measured over a circular aperture of diameter 2′′? | ||
| + | |||
(T8.3) In practice, only 20% of U-band photons falling on the primary mirror are detected. How many | (T8.3) In practice, only 20% of U-band photons falling on the primary mirror are detected. How many | ||
photons, 𝑁<sub>t</sub> | photons, 𝑁<sub>t</sub> | ||
2019年9月11日 (三) 17:40的版本
英文题目
(T8) U-Band photometry
A star has an apparent magnitude 𝑚U = 15.0 in the U-band. The U-band filter is ideal, i.e., it has perfect (100%) transmission within the band and is completely opaque (0% transmission) outside the band. The filter is centered at 360 nm, and has a width of 80 nm. It is assumed that the star also has a flat energy spectrum with respect to frequency. The conversion between magnitude, 𝑚, in any band and flux density, 𝑓, of a star in Jansky (1 Jy = 1 × 10−26 W Hz −1 m−2 ) is given by
𝑓 = 3631 × 10−0.4𝑚Jy
(T8.1) Approximately how many U-band photons, 𝑁0 , from this star will be incident normally on a 1 m2 area at the top of the Earth's atmosphere every second?
This star is being observed in the U-band using a ground based telescope, whose primary mirror has a diameter of 2.0 m. Atmospheric extinction in U-band during the observation is 50%. You may assume that the seeing is diffraction limited. Average surface brightness of night sky in U-band was measured to be 22.0 mag/arcsec2 .
(T8.2) What is the ratio, 𝑅, of number of photons received per second from the star to that received from the sky, when measured over a circular aperture of diameter 2′′?
(T8.3) In practice, only 20% of U-band photons falling on the primary mirror are detected. How many photons, 𝑁t , from the star are detected per second?
