【单选题】
平面的正面投影积聚为一条直线并与OX轴平行，该平面是（ ）。
①
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:普通表格;
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin:0cm;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.5pt;
mso-bidi-font-size:11.0pt;
font-family:等线;
mso-ascii-font-family:等线;
mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:等线;
mso-fareast-theme-font:minor-fareast;
mso-hansi-font-family:等线;
mso-hansi-theme-font:minor-latin;
mso-font-kerning:1.0pt;}
正平面
②
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:普通表格;
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin:0cm;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.5pt;
mso-bidi-font-size:11.0pt;
font-family:等线;
mso-ascii-font-family:等线;
mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:等线;
mso-fareast-theme-font:minor-fareast;
mso-hansi-font-family:等线;
mso-hansi-theme-font:minor-latin;
mso-font-kerning:1.0pt;}
水平面
③
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:普通表格;
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin:0cm;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.5pt;
mso-bidi-font-size:11.0pt;
font-family:等线;
mso-ascii-font-family:等线;
mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:等线;
mso-fareast-theme-font:minor-fareast;
mso-hansi-font-family:等线;
mso-hansi-theme-font:minor-latin;
mso-font-kerning:1.0pt;}
正垂面
④
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:普通表格;
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin:0cm;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.5pt;
mso-bidi-font-size:11.0pt;
font-family:等线;
mso-ascii-font-family:等线;
mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:等线;
mso-fareast-theme-font:minor-fareast;
mso-hansi-font-family:等线;
mso-hansi-theme-font:minor-latin;
mso-font-kerning:1.0pt;}
铅垂面
【单选题】
黑板上“等号”的两条平行线段距离为D，设人的瞳孔直径为d，光的波长为λ，则人在距离黑板（）处刚好可分辨出黑板上的等号。
①
D/1.22d
②
D/0.61d
③
Dd/1.22d
④
Dd/0.61d