interference of light

[Primarygun]

Why interference still occurs when a beam of red light passes through a hole created by the slits? The screen captures different brightness of red light.

If there are no interferences took place, the brightness should be uniform.

[swansont]

Could you clarify what you mean by "a hole created by the slits?"

[Primarygun]

--- Hole ------ slit

 

--------------Wave

--------------Wave

 

The situation as if this one represents.

[swansont]

So there's basically two slits of differing sizes? You should still get interference. But with a hole that's very wide you will probably lose contrast. Diffraction effects come into play when you look at the slit/hole sizes. As the hole gets big the diffraction peak gets narrow, and you won't see the higher interference orders.