问题 问答题

如图所示为研究光的反射规律的实验装置.把一个平面镜放在水平桌面上,再把一张纸ENF、竖直地立在平面镜上,纸板上的直线ON垂直于镜面.

(1)一束光EO沿着纸板上的某一个角度射向O点,经平面镜反射,沿另一个方向OF射出.为了探究反射角和入射角的关系,应该在纸板上用笔描出入射光线和反射光线的径迹,测出______和______的大小(用图甲中的字母表示).

(2)改变光线的传播方向,再做两次实验,记录的实验数据表格如下.

实验序号入射角反射角
150°50°
240°40°
320°20°
分析数据可以得出:反射角______入射角,反射角随着入射角的增大而______.

(3)把纸板NOF向前折或向后折(如图乙所示),还能看到反射光吗?______.

答案

(1)实验中,我们所研究的入射角是指入射光线与法线的夹角,反射角是指反射光线与法线的夹角,因此,读图可知,我们应测出∠E0N和∠NOF的大小;

(2)表格数据表明,入射角分别为50°、40°、20°时,反射角也是相同的度数,并且反射角随着入射角的增大而增大;

(3)图乙中,当把纸板NOF向前折或向后折时,无法看到反射光线,这表明反射光线和入射光线、法线是在同一平面内的.

故答案为:(1)∠E0N,∠NOF;

(2)等于,增大;

(3)不能.

阅读理解

阅读理解。

    Pocket Tape-Recorders"Family and Home Magazine"test what's on the market now.

1)Pearlcorder S702 $64

  This simple model at the bottom of the Olympus range scored the most points for its excellent quality of recording. Background noise hardly affects the sound and recording from a pocket is perfectly possible, but it doesn't turn off automatically.

Tape length: 30 minutes per side. Weight:240g.

2)Sony M9 $49.95

    Small and very good looking, sony's latest offering scored most for appearance. Sounds clear, but there is slight machine noise. The big control buttons are a great improvement on some of the complicated little controls on other tape-recorders. Doesn't switch off automatically but a red light shows if the machine is still running.

   Tape length: 60 minutes per side. Weight: 195g.

3)Sony M400 $115

    Lots of little control buttons that make a noise and are difficult to use . Recording was good but machine noise lost points. Tape counter and automatic switch-off when tape has finished recording or rewinding are useful Tape length: 60 minutes per side. Weight: 230g.

4)Imperial OEM. MC $29.95

    Cheap and simple compared with the rest, but recording was good as long as there was no background noise. Use only its own make of cassette. No light to show it is on; no fast forward button and the record button makes a loud noise.

    Tape length: 30 minutes per side. Weight: 285g.

5)Philips 585 $80

   Handsome and simple to use, but recording is very poor at more than the recommended distance of 5 cm-designed for dictation. No recording light. Tape length: 15 minutes per side. Weight: 220g.

1.The machine that produces the best recording with the least unwanted noise is the           .

A.Pearlcorder S702  

B.Sony M9    

C.Sony M400

D.Imperial OEM MC7

2.It you want a machine which turns off automatically and weighs very little you should choose the          .

A.Pearlcorder S702    

B.Sony M9    

C.Sony M400

D.Philips 585

3.Which machine is unsuitable for general use?

A.Pearlcorder S702

B.Imperial OEM MC7

C.Sony M400

D.Philips 585

4.What disadvantage does only the Imperial OEM MC7 have?

A.No light shows when it is on

B.It requires a special cassette.

C.It picks up background noise.

D.The record button makes a noise.

选择题