题目内容

波长为λ的单色平行光，垂直照射到宽度为 b 的单缝上，若衍射角φ=30°时，对应的衍射图样为第一级极小，则缝宽 b 为

A. λ/2
B. λ
C. 2λ
D. 3λ

查看答案

搜索结果不匹配？点我反馈

更多问题

___________ students may set up a lion dance.

American
B. Korean
Chinese
D. British

The Paper Scissors Stone Club was founded in ____ .

A. Paris
B. Tokyo
C. Beijing
D. London

In China，the earliest printed poster appeared in_____ Dynasty.

A. Ming
B. Song
C. Qing
D. Tang

There are usually ____ elements involved in a poster.

A. six
B. five
C. four
D. three