Answer :
1. The property of light travelling in straight lines which is rectilinear propagation of light. As it does not scatter all over the place, a strong parallel beam is obtained on the screen.
2. When the light falls on the screen it is reflected back to our eyes which enables us to see.
2. When the light falls on the screen it is reflected back to our eyes which enables us to see.
the reflection cause this property to see the path of light in the darkness of a cinema hall