The help of scientific homework

Firstly, point out the optical principle of "shadow" in the following sentences:

1) photography (refraction of light); 2) showing movies (straight-line propagation of light);

3) Direct result (straight line propagation of light); 4) Reflection in water (reflection of light);

Second, Xiao Bin went to the photo studio to take photos. He took a full-length photo first, and then asked for a bust. If Xiao Bin doesn't move, the photographer can (move forward) fill in a few steps, or the photographer (retract) ("retract" or "extend") the camera lens a little.