Question

Why light cannot travel through opaque objects and why they can travel through transparent object ?

Answer 1

Opaque materials do not allow transmission of light waves. Inother words, we can't see through an opaque object. We can only see the surface because the light waves are re-emitted from the surface back to our eyes. Opacity occurs because of the reflection of lightwaves off the surface of an object.
The transparency and opacity of objects depends on how light waves interact with the materials of those object . Light waves cause vibrations in surface atoms, which are either absorbed, transmitted or reflected. ... Therefore, opacity is caused by the reflection of light waves.