Final answer:
Turning on a light when entering a room is a physical change that involves electricity instantaneously activating a light source. It's a straightforward process where light shines due to the electrical flow, akin to nerve impulses in the body, and is affected by the physical structure of openings like windows and doors.
Step-by-step explanation:
Turning on the light to look around constitutes a physical change. A physical change involves altering the physical properties of a substance or object without changing its identity. In this instance, when the person enters the house and turns on the light, they are initiating an electrical process that causes the light to shine. The electricity flows through wires, reaching the bulb and producing light instantly, similar to how nerve impulses travel through the body's network of nerves.
Windows and doors control what enters and leaves a house. In the case of light shining through an open door into a dark room, we expect to see a sharp shadow of the doorway. This is due to the light waves travelling in straight lines until they hit an obstacle or pass through an opening. However, interesting phenomena such as diffraction can occur when light passes through small openings, leading to some bending around corners, although this effect might not be noticeable in everyday situations like turning on a light in a room.