在均匀磁场B内放置一极薄的金属片，其红限波长为l0。今用单色光照射，发现有电子放出，有些放出的电子(质量为m，电荷的绝对值为e)在垂直于磁场的平面内作半径为R的圆周运动，那末此照射光光子的能量是：
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 如图所示电路的逻辑表达式F=（ ）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/8655693a417e4e43a32e0732ed533c96.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/beda73211aea49f082d9137fd4eb0526.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7388c99ee0824f20bcf85893934a2f6a.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/9a5c81e78b344c79a9389e932a7f55ce.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/82193a9a030243728012b02e15718987.png" />
- 体系处于<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7bae90aad0f0442d9d6adf4ff4c69c2c.png" />状态,则体系的动量取值为 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/156065cb1de5431a9a2ea0b029f26f79.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/627120343f054317828addfe01200e5b.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/09f88938fc6f43a0819284117c0b14fa.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/2311487532fb45c789f7dce939291db1.png" />
- 一维谐振子处于<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7117096d5bb94d5abc582889ebf7ad5d.png" />态中,则该谐振子能量取值分别为 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/cb815c204bbb46ec8279a3382b927106.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/fce0d76351cb404da913e76852c23f0f.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/b67a8f55418347e78d9fe5fc37d245a8.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/de94246b2e7b4f57a297ff91789ec026.png" />
- 如图示并联管路，已知各支路的沿程阻力系数之比为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/6e209020d20f4543823ce6516ae8ca06.png" />，管长之比为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/50814fe028094040bc955d8e1542b6d2.png" />，且<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/40b4c6a9565b483590c5c7d607e7ed66.png" />，则两支管的流量之比<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1055534bfce6426a94682ba086a5b17e.png" />=（）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/77815369f5cd41f3a2e68b9524b454c5.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/0cd231eebe45465f941a0f614743e6d2.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7555afa5223e40bf89ca575cf7b52754.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1b06cd474b844644a6d97ad87d208e94.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/d0b2bca045414236a7d1c9925a9264f2.png" />
- 在定温边界条件下，稳态、无内热源、导热系数为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/bf35cea9e03449f0b64673e21dbdde56.png" />、内外径分别为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/3323de11627a4f51bc7b1fff540dcfef.png" />和<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/675dd37c97db44a7a723838858eab505.png" />、长度为l的单层圆筒壁的导热热阻为（）。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/892cb3300ea148d994377392a697acb0.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7003425fa14a44d5aadbb9040240edca.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/040ff55c3a244877a0b06faf6042f47a.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/b5d2a5ed4d644ae6b2dab35d2ed8f3e5.png" />