This is a collection of exercises to be carried out on the web or on the classroom computers. Their intent is to show you a range of numerical answers associated with different physical phenomena; these are the type of calculations which are carried out in the problem-solving type physics courses. In the case of these exercises, the actual calculations are done by the computer but it is hoped that the exercises will help you become accustomed to the computer as a tool and a source of information.

这些练习可以在网络上或教室的电脑上进行。其目的是向你展示与不同物理现象相关的各种数值答案；这些就是问题解决型物理课程中进行的计算类型。在这些练习中，实际的计算由计算机完成，但希望这些练习能帮助你逐渐适应计算机作为工具和信息来源的角色。

You will be informed in class about when exercises are due to be turned in. They will be logged and returned to you. It would be a good idea to work on the exercises as soon as we have covered the material in class so you won't have to do them all in a rush when they are called for.

你们将在课堂上被告知作业的截止日期。这些作业会被记录并退还给你们。最好在我们讲完相关材料后尽快完成作业，这样在截止日期临近时就不会显得匆忙了。

A link to the exercises may be found in the right-hand column on the Physics 7120 Calendar. Links in the exercises will take you to the calculation in HyperPhysics.

在物理学7120日历的右侧列中可以找到练习题的链接。练习题中的链接将带你进入HyperPhysics进行计算。

Note about entering numbers in calculations: When you enter a number in one of the calculations in HyperPhysics, you then just click anywhere outside the box to make sure the transaction is complete and the number is taken. If you need to edit the number, it is usually easiest to just double-click in the data entry box. That will turn the field dark, and any number you type will replace the previous number.

关于在计算中输入数字的说明：当你在HyperPhysics中的某个计算中输入一个数字时，只需点击框外的任何地方以确保交易完成，数字将被采纳。如果需要编辑数字，通常最简单的方法是双击数据输入框。这会将字段变暗，你输入的任何数字都将替换之前的数字。

练习1：波的计算

1. What is the wavelength in meters of the electromagnetic carrier wave transmitted by the radio station WSB AM at 750 kHz? 1 kHz =10³ Hz and the speed of light is 3 x 10⁸ m/s.

无线电电台WSB AM在750 kHz频率上传输的电磁载波波长是多少米？1 kHz=10³ Hz，光速为3×10⁸ m/s。

2. What is the wavelength in meters of the electromagnetic carrier wave transmitted by GSU's WRAS at 88.5 MHz ? 1 MHz = 10⁶ Hz

2. GSU的WRAS发射的电磁波波长是多少米？1 MHz = 10⁶ Hz

3. If a sound is produced at the orchestra standard frequency of 440 Hz, at a temperature where the speed of sound is 345 m/s, what is the wavelength of the sound produced?

如果在标准音乐会音高440 Hz下产生声音，温度下声音的速率为345 m/s，所产生的声音的波长是多少？

4. If the limits of human hearing are 20 Hz to 20,000 Hz, what are the sound wavelengths associated with these extremes. You may use 345 m/s for the speed of sound.

4. 如果人类的听觉范围是20 Hz到20000 Hz，这些极值对应的声波波长是多少？你可以使用345 m/s作为声速。

Exercise 2: Open air column resonance
1. If a flute constitutes an open air column, how long must the air column be if it is to produce a frequency at middle-C, 261 Hz?

练习2：开放空气柱的共振 1. 如果一个 flute 构成一个开放空气柱，那么要使其产生中音C（261 Hz）的频率，这个空气柱的长度必须是多少？

2. An open-ended organ pipe is to be constructed to sound the note A= 55 Hz, one octave above the bottom note on the piano. How long must the air column be?

要构造一个开口的管风琴管，使其能发出A=55 Hz的音调，该音调比钢琴最低音高一个八度。空气柱必须有多长？

练习3: 闭合空气柱共振

1. A clarinet acts as a closed-ended air column. If its bottom note has a frequency of 130 Hz, how long is the column?

1. 一种圆号相当于一个封闭的空气柱。如果它的最低音频率为130 Hz，这个空气柱有多长？

2. The ear canal responds most strongly to frequencies around 3700 Hz because that is the lowest resonant frequency of the canal. If the canal acts like a closed-ended cylinder, how long is the ear canal?

耳道对约3700 Hz的频率响应最强，因为这是耳道的最低共振频率。如果耳道可以看作是一个封闭的圆柱体，那么耳道有多长？

3. If the top resonance of the water tube resonance unit is at a column length of 8 cm when a tuning fork of frequency 1024 Hz , what is the corresponding speed of sound?

如果水柱共振器的最高共振频率对应于8厘米的柱长，当使用频率为1024 Hz的音叉时，求相应的声速？

Exercise 4: Formation of real images
1. If a camera lens has a focal length of f = 5 cm, at what image distance from the lens must the film be placed to form an image of an object which is 500 cm from the lens?

练习4：实像的形成 1. 如果一个相机镜头的焦距为 f = 5 cm，当物体距离镜头500 cm时， film 应放置在距离镜头多少厘米处以形成物体的像？

2. If the object is moved closer to the camera lens ( to 100 cm) what is the distance to the film from the lens?

如果物体被移近相机镜头（至100厘米），则镜头到胶片的距离是多少？

3. If you want to take a picture of a flower at only 20 cm from the lens, what lens-to-film image distance would be required? (This probably would require and extension tube).

如果你想拍摄一朵距离镜头仅20厘米的花，所需的镜头到底片的像距是多少？（这可能需要使用延长管。）

4. In a slide projector the slide is placed very close to the focal length of the lens. If you want to project an image 5 meters away from a f=5cm slide projector lens, where would you have to put the slide (object distance)?

在幻灯机中，幻灯片被放置在透镜的焦距非常接近的位置。如果你希望用一个f=5cm的透镜将图像投射到5米远处，幻灯片（物距）应该放在哪里？

练习5：虚像的形成

1. If you are looking through a divergine lens of focal length f = -20 cm at an object which is 40 cm away from the lens, at what distance from the lens would the image appear to be?

如果你通过一个焦距为 f = -20 cm 的发散透镜观察一个距离透镜 40 cm 的物体，图像会出现在距离透镜多远的位置？

练习6：更多的虚拟像

If the object distance is smaller than the focal length of a magnifying lens, then the image will be virtual, on the same side of the lens as the object and further away.

如果物体距离小于放大透镜的焦距，那么像将是虚像，位于透镜与物体同侧，并且更远离透镜。

1. If you use a magnifier of focal length f=10 cm to look at an object which is at 5 cm from the lens, where will the image appear to be? What will be the magnification?

如果你使用一个焦距为 f=10 厘米的放大镜来观察一个距离透镜 5 厘米的物体，图像会出现在哪里？放大率是多少？

2. If you put the object closer to the focal length, at 9 cm from the lens, where will the image be and what is its magnification?

如果将物体放在距离透镜9厘米处，像会出现在哪里？其放大率是多少？

Exercise 7: Atomic Spectra
Radiation of all the types in the electromagnetic spectrum can come from the atoms of different elements. A rough classification of some of the types of radiation by wavelength is:
Infrared   > 750 nm
Visible   400 - 750 nm
Ultraviolet   10-400 nm
Xrays   < 10 nm
(An approximate classification of spectral colors: Violet (380-435nm), Blue(435-500 nm), Cyan (500-520 nm), Green (520-565 nm), Yellow (565- 590 nm), Orange (590-625 nm), Red (625-740 nm).
1. If the electron in a hydrogen atom (Z=1) makes a transition from n=2 to n=1, the wavelength of the radiation will be _______ nm, which is in the __________ part of the electromagnetic spectrum.
2. If the electron in a hydrogen atom (Z=1) makes a transition from n=3 to n=2, the wavelength of the radiation will be _______ nm, which is in the __________ part of the electromagnetic spectrum.
1. If the electron in a hydrogen atom (Z=1) makes a transition from n=4 to n=3, the wavelength of the radiation will be _______ nm, which is in the __________ part of the electromagnetic spectrum.
1. If the electron in a oxygen atom (Z=8) makes a transition from n=2 to n=1, the wavelength of the radiation will be _______ nm, which is in the __________ part of the electromagnetic spectrum.

练习7：原子光谱电磁谱中所有类型的辐射都可以来自不同元素的原子。按波长粗略分类的一些辐射类型是：红外线>750 nm 可见光 400-750 nm 紫外线 10-400 nm X射线<10 nm（近似颜色光谱分类：紫（380-435nm），蓝（435-500 nm），青（500-520 nm），绿（520-565 nm），黄（565-590 nm），橙（590-625 nm），红（625-740 nm）。1. 如果氢原子（Z=1）中的电子从n=2跃迁到n=1，辐射的波长将是______ nm，位于电磁谱的________部分。2. 如果氢原子（Z=1）中的电子从n=3跃迁到n=2，辐射的波长将是______ nm，位于电磁谱的________部分。3. 如果氢原子（Z=1）中的电子从n=4跃迁到n=3，辐射的波长将是______ nm，位于电磁谱的________部分。4. 如果氧原子（Z=8）中的电子从n=2跃迁到n=1，辐射的波长将是______ nm，位于电磁谱的________部分。

Exercise 8: Radioactive half-life
1. If the half-life of a certain radioisotope is 1 year, what fraction of it will remain after 3 years? _____________
2. For carbon-14 with a half-life of 5730 years, how long will it take to decay to one-tenth of its original activity? _____________
3. Iodine-131 has a half-life of 8 days. If a given contamination is considered tolerable when it has decayed to one-thousandth (0.001) of its original value, how long would that take? _____________
4. Cesium-137, the most insidious of the contaminants released at Chernobyl, has a half-life of 30 years. If it must reduce to one-thousandth of its initial value, how long would that take? _____________

练习8：放射性半衰期 1. 如果某种放射性同位素的半衰期为1年，那么3年后剩余的分数是多少？_____________ 2. 对于碳-14，其半衰期为5730年，要衰变到原始活度的十分之一，需要多长时间？_____________ 3. 碘-131的半衰期为8天。如果某次污染被认为可接受的条件是其衰变到原始值的千分之一（0.001），那么需要多长时间？_____________ 4. 铀-137，是切尔诺贝利事故中释放出的最危险的污染物之一，其半衰期为30年。如果它必须衰变到初始值的千分之一，需要多长时间？_____________