光的性質 波長 頻率 光速 光子能量 偏振
700 nm 600 500 400
E= hv = hc/l 光子能量 化學鍵強度 kcal/mol 波長, nm UV is important in Vitamin D synthesis, DNA damage, … 光子能量 化學鍵強度 kcal/mol UV-B UV-C UV-A 波長, nm
Diffraction Grating 光柵 蘇曼儂、林志民 Research Assistant, Institute of Atomic and Molecular Sciences Academia Sinica, Taipei, Taiwan 10617
Different types of grating surface
p = 180o p 2p
a d d sin a
b d d sin b
光程差= d sin a + d sin b 建設性干涉條件 m = 0, 1, 2, 3, ... -1, -2, -3, ...
Excel Demo
m = 0, 1, 2, 3, ... m = 0, 光程差= d sin a + d sin b 建設性干涉條件 -1, -2, -3, ... m = 0, 符合巨觀之反射定律 a -b
Other illustrations
d = 1.6 m m for CD, 0.74 m m for DVD m=1, d = 1600 nm To simplify the problem, let’s first assume sin a is a constant. m=1, d = 1600 nm l sin a + sin b = l/d 400 nm 0.25 533 nm 0.33 700 nm 0.44
Slit Width and Angular Resolution 1.4 mm 80 mm
In this practical case, sin a and sin b are variables. m=0 m=1 CD In this practical case, sin a and sin b are variables. Note sin b changes more with wavelength than sin a.
CD 自動數位相機很難對焦 (它對人臉對焦比較行)
DVD (終於對到焦點了!)
DVD
DVD
Ocean Optics USB2000+UV-VIS-ES 611 546 542 436 577 579 404 Ocean Optics USB2000+UV-VIS-ES
movie
Acknowledgement 游大立老師 設計 中央研究院天文及天文物理研究所 印製 簡易摺紙光譜儀