A water, oil emulsion is a non-homogeneous mixture of water and oil, held together by an emulsifier (a substance that stabilizes an emulsion, in particular an additive used to stabilize processed foods) , like egg! If you shine a laser beam through a beaker of this emulsion, it will surely travel in a straight line.
False. As the water oil emulsion is not homogeneous, it is not the same medium that light is travelling through! The local properties of the mixture are varying, so, the beam is continuously changing medium from water to oil etc etc, therefore, it will, in general not travel in a straight line!
Ok, the physics is done and dusted, now, let's learn some stuff about emulsions:
Take a cup of water and a cup of oil, and combine them into a third cup. Instead of the two liquids mixing together, the oil will just float on top of the water. Even if they are mixed together, the oil and water quickly separate again. Next beat up an egg and mix it with the oil and water. Now the oil and water aren't separating. Why is this? How is this possible? An emulsion is a mixture in which the substances combined are not soluble with each other. The substances will not mix or stay mixed with each other without the help of an emulsifier. In the water and oil emulsion, the egg is the emulsifier (now what exactly the egg does is for you to find out!). Now, this emulsion is not homogeneous, meaning its composition will not be uniform everywhere.