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【简答题】
铁路信号按信号机具是否可以移动分为哪几类？
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】在宽度为a=0.60mm的狭缝后放置一焦距f=40cm的会聚透镜，若以单色平行光垂直照射狭缝，则在置于透镜主焦平面处的屏幕上x=1.4mm处的P点看到衍射明条纹，求 (1)入射光的波长以及P点衍射条纹的级数； (2)在该衍射条件下，缝面可分成的半波带数； (3)中央明条纹的宽度以及第二级明纹对应的衍射角。
【简答题】利用波长为λ=0.59μm的平行单色光照射光栅，已知光栅上每毫米宽度内刻500条狭缝，透光狭缝宽度a=1×10 -3 mm．试求：
【简答题】在单色器的线色散率为0.5mm/nm的条件下用原子吸收分析法测定铁时，要求通带宽度为0.1nm，狭缝宽度要调到______。
【单选题】下列有关准直器的描述，错误的是
A.
准直器狭缝宽度决定线束宽度
B.
准直器狭缝宽度决定扫描层厚
C.
准直器窗口呈狭缝状态
D.
准直器狭缝宽度决定扫描层距
E.
准直器位于X线窗口前端
【单选题】Choose the best item to complete each of the following sentences. 7. He always ______ the latest fashions.
A.
commented
B.
appeared
C.
followed
D.
attempted
【单选题】Choose the best item to complete each of the following sentence. 7. Does art ______ society, or shape it?
A.
mirror
B.
admit
C.
inspect
D.
claim
【单选题】Choose the best item to complete each of the following sentences. 1、 There’s no supermarket in the _____ area.
A.
immediate
B.
temporary
C.
recent
D.
brief
【单选题】Choose the best item to complete each of the following sentences. 4. Wearing long skirts has become very ______ recently.
A.
frequent
B.
popular
C.
famous
D.
average
【单选题】Choose the best item to complete each of the following sentence. 6.This sentence doesn't make any______.
A.
benefit
B.
sense
C.
help
D.
meaning
相关题目：
【单选题】下列有关准直器的描述，错误的是
A.
准直器狭缝宽度决定线束宽度
B.
准直器狭缝宽度决定扫描层厚
C.
准直器窗口呈狭缝状态
D.
准直器狭缝宽度决定扫描层距
E.
准直器位于X线窗口前端