We see a body if it emits light, or if it is illuminated.
All the celestial bodies we see with the naked eye in the clear night sky are lights.
A light source must be heated to a high enough temperature to emit light.
The speed of light propagation depends on the substance through which it propagates.
Light propagates rectilinearly within the same matter
with respect to the vertical. At what angle to the vertical will it reflect?
with respect to the plane of the mirror and is reflected. What is the angle between the incident and reflected rays?
?
and write down how much it measures (measure it with a geotriangle).
. How much is the angle of reflection?
of the image against the focal length 
of the mirror. Describe the image of the object.
