I am doing a physics project where I have to explain the physics behind my instrument I make, I am making an harmonica out of straws(like the picture). Why do the different size straws make different sounds?

Because different size straws have different frequency.

Explanation: A shorter straw should have made a sound wave with a higher frequency than a longer straw, and so shorter straws should have made a higher pitch than longer straws.

electrical power

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.