2. We divide objets in to three groups depending on
how much light can pass trougth them

3.  Like clear glass bottles allow light to pass
througth

4.  Allow some light to pass through

5. For example wood and cardboard, do not allow
light to pass through

6.  Some objets do not let light through . When
light cannot travel through an objet, a shadow
is formed on the opposite side to the source of
light.