问题
选择题
一束光线入射到平面镜上发生反射，若反射光线与镜面的夹角为30°，则入射角为（ ）
A．30°
B．60°
C．45°
D．90°
答案
已知反射光线与镜面的夹角为30°，因此反射角为90°-30°=60°，由反射定律可知，反射角的等于入射角，故入射角也等于60°．
故选B．
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一束光线入射到平面镜上发生反射，若反射光线与镜面的夹角为30°，则入射角为（ ）
A．30°
B．60°
C．45°
D．90°
已知反射光线与镜面的夹角为30°，因此反射角为90°-30°=60°，由反射定律可知，反射角的等于入射角，故入射角也等于60°．
故选B．
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| Mr. Johnson was having trouble with his stomach. 1 he went to see a doctor. The doctor examined his stomach 2 but couldn't find any problem. Then he said,"Well,Mr. Johnson,take it 3 . There's 4 serious,stop 5 and then you'll be all right very 6 ." "But doctor," answered Mr. Johnson,"I 7 ,and I don't like smoking 8 " "Oh,I see, " said the doctor,"then stop drinking alcohol (酒) 9 ." "But I don't drink alcohol," answered Mr. Johnson. "Don't drink 10 tea or coffee then," the doctor said 11 him. "I 12 drink water," answered Mr. Johnson,"I don't like tea or coffee, 13 The doctor 14 for a while and then said,"Well,what do you like to eat then?" "Potatoes,I like potatoes very much," Mr. Johnson answered at once. "All right,then stop 15 potatoes," said the doctor as Mr. Johnson got up to say goodbye to him. | ||||
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