About
An open source physics at Singapore simulation based on codes written by Fu-Kwun Hwang and Loo Kang WEE.
more resources can be found here
http://iwant2study.org/ospsg/index.php/interactive-resources/physics/04-waves

Introduction
The intensity of the image for the object is reduced is some light path were blocked (the whole image is still there).
Select from drop-down menu or drag to "block part of light path" button or drag lower end of the black line to lower position to block part of light paths.
The intensity is not the same if part of the light paths were blocked.
You can change the slit position and its width with mouse drag.

Interesting Fact
There is a common misconception among students:
Blocking part of the lens surface would block the corresponding part of the image. With this app, it is easier to explain and understand.

Acknowledgement
My sincere gratitude for the tireless contributions of Francisco Esquembre, Fu-Kwun Hwang, Wolfgang Christian, Félix Jesús Garcia Clemente, Anne Cox, Andrew Duffy, Todd Timberlake and many more in the Open Source Physics community. I have designed much of the above based on their ideas and insights, and I thank the OSP community for which Singapore was honored with 2015-6 UNESCO King Hamad Bin Isa Al-Khalifa Prize for the Use of ICTs in Education.