Question

Why does transparent object allow light to pass through it?

Answer 1

Because it do not polish by sliver or aluminium layer due to which molecule of tra
nsparent object attract towards light partical itself.

Answer 2

Hey janhnavi
Actually if light passes through any medium only then it is known as transparent. And
The incoming light interacts with the material (the electrons are excited by the electro magnetic field of the light). In every (crystal) layer of the material light is absorbed and re-emitted again with a phase lag.

If the phase lag is not very large (~90 degrees) the material is transparent. The effect of the phase lag is visible by dispersion. The phase lag is relatively larger for short wavelengths (blue) than for longer wavelengths (red). Red light is less affected and will bend less than blue light.

Translucent materials have a phase lag of ~180 degrees. In these cases the emitted light will extinguish the original light (destructive interference). This effect is not immediate -- the light is will be extinguished as it progresses through the material.

Opaque materials don't re-emit light as much. The energy stays in the material, causing it to warm up. In other cases the light is reflected diffusively: in all directions.
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Lokesh C M
Lokesh C M, BSc Ph.D. in Physics & Civil Services Exam of India, BGS Degree College (2018)
Answered Feb 13
Hello,

Opaque materials do not allow transmission of light waves. In other 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 light waves off the surface of an object .

And also,

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.

Thank you,

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Paul Woods
Paul Woods, MA Theoretical Physics & Computer Science, University of Cambridge (2008)
Answered Dec 8, 2014
Because I'm not convinced that the previous explanation, which focussed on phase, is particularly explanatory for this question, I thought I'd point to a lecture where these things are explained very neatly. If you don't have enough physics, you can back-track from this point through this excellent series of lectures to get up to speed. The explanation is very interesting, and the comparison between diamond and copper is particularly enlightening (please pardon the unavoidable puns).

A short explanation is near-impossible, but very roughly: there must be, within the structure of a transparent material, ranges between gaps between permitted electron energy levels sufficient that electric dipoles are present of energy range (and thus frequency range) of the visible spectrum, thus permitting electromagnetic activity within the material at visible light frequencies