题目

氢原子处于基态时，原子的能级为E1 =－13.6eV，普郎克常量h = 6.63×10－34J·s，氢原子在n = 4的激发态时，问：    （1）要使氢原子电离，入射光子的最小能量是多少？    （2）能放出的光子的最大能量是多少？ 答案：（1）0.85eV （2）12.75eV 解析:1） 使氢原子电离需要的最小能量E = 0.85eV    （2）从n = 4能级跃迁到n = 1能级时，辐射的光子能量最大     △E = E4－E1 = 12.75eV阅读理解。       There are forty-eight students in our class. There are twenty- three boys and twenty- five girls. Some   students live near the school, and some others live very far from the school About half of the students   come to school by bike. They often get to school at a quarter to seven. About ten students often come to   school by bus. They often go to school very early, too. Another ten students come to school on foot.   Their homes are near the school, but they are often late for school, because they get up very late.根据短文内容，选择正确答案。1. More than half of the students usually come to school _____.A. very late     B. very early         C. by bus2. Some students are often late for school because _____.A. their homes are far from the schoolB. they go to school on footC. they get up very late3. About _____ students go to school by bike.A. forty-eight   B. ten         C. twenty4. About ten students often come to school by bus because _____.A. their homes are not near the schoolB. they don't have any bikesC. they can't ride bike5. How many students live far from the school?A. About thirty-eight .B. About twenty.  C. About ten.