Design a SIMPLE experiment showing this case:?

Question

To show that light unlike sound, does not need a substance such as air in which to travel.

Answer 1

Put a clear plastic bag wrapped and taped tightly over the end of a flashlight.

Answer 2

Well the simplest would be to go outside and look at the stars, or notice the sun light, depending on the time of day (if it is daylight, don't look directly at the sun) Of couse this assumes that you can establish that there is nothing significant between the Earth and stars (or sun)

If you have a transparent contanier and a vacuum pump, you could design a not so simple experiment, but simple is a problem.