Light energy moves in the form of waves. Light can travel through a vacuum. Light waves cannot be seen. Ray or beam of light can be seen clearly if there are particles in the surrounding that reflect the light into our eyes. Light from a light source goes out in all direction in straight lines. If an opaque object blocks the path of the light, it cannot pass through. A dark patch or image of the object is formed at the opposite side of the light source. This dark image is called a shadow. Many events or phenomena that occur naturally can be used to show that light travels in a straight line. Examples are light from a light house, light going out from a torch or street lamp, a ray of light pass through from a hole on the roof on a sunny day and light from a bright room enters a dark room through a small opening or partially opened door.
Light from a light house
Light going out from a torch
Light going out from a street lamp
Light pass through from a hole