已知光在真空中的传播速度C=3×108m/s。如图，折射率n＝1.5某玻璃立方体放在空气中。光线从立方体的顶面斜射进来，然后投射到它的另一个侧面P点，问：
① 光在玻璃中的传播速度V；
②此光线能否从另一个侧面P点射出？请说明你判断的依据。
①2×108 (m/s)②光线不能在P点射出
① 光在玻璃中的传播速度V
V="C" / n =3×108 / 1.5 (m/s)= 2×108 (m/s) (1分)
② 该玻璃发生全反射的临界角C
故C<450 (1分)
光线在B点发生折射，由折射定律知
故r<450 (1分)
由几何关系知i1=900-r>450 >C (1分)
所以光线在P点一定发生全反射，
光线不能在P点射出 (1分)
| 阅读理解。 | |||
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| 1. After taking the course at www. ASRLCT.org, you will be able to . | |||
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| A. travel for little or no money B. get more tickets C. keep learning D. work on the ship | |||
| 2. If you visit the USA Pavilion in early afternoon, ______. | |||
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| A. you can visit it for free B. you can visit it in 35 minutes C. it will take you less time to enter D. it will be much easier to find Gate No 8 | |||
| 3. We can go to visit the Body Image Exhibition ______. | |||
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| A. at 4:30 p.m. B. at night C. for free D. at 325 Nanjing Road W |