问题
选择题
一束光跟平面镜之间的夹角是40°，则（ ）
A．入射角为40°
B．反射角为50°
C．反射角为40°
D．反射光线和入射光线的夹角为80°
答案
光线与平面镜成40°角射向平面镜，则入射角=90°-40°=50°，反射角也是50°，反射光线与入射光线的夹角等于入射角和反射角的和，即夹角为50°+50°=100°．
故选B．
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一束光跟平面镜之间的夹角是40°，则（ ）
A．入射角为40°
B．反射角为50°
C．反射角为40°
D．反射光线和入射光线的夹角为80°
光线与平面镜成40°角射向平面镜，则入射角=90°-40°=50°，反射角也是50°，反射光线与入射光线的夹角等于入射角和反射角的和，即夹角为50°+50°=100°．
故选B．
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