为了探究光的反射定律,小明准备了一块平面镜、一块画有ON的平整白色硬纸板、直尺、量角器及铅笔,计划组装成如图所示的装置进行实验.
(1)这个实验还需要的一个重要器材是 ____;
(2)如果纸板与平面镜不垂直,入射光沿纸板照射后将会出现的现象是 ____
—Have you read the book Harry Potter?
—Sure. Eric is also it and we become friends because of that.
hào zhào
nuò yán
dǎn qiè
zhū wèi
wán bì ɡuī zhào
fù jīnɡ qǐnɡ zuì
____
如图,AB为半圆O的直径,弦AD、BC相交于点P,若CD=3,AB=4,则tan∠BPD等于( )