Question

A group of students took an old shoe box and covered it with a black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the light. They placed a milk sample contained in a beaker/tumbler in the box as shown in the Fig.2.4. They were amazed to see that milk taken in the tumbler was

illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it? 

(a) Explain why the milk sample was illuminated. Name the phenomenon involved. 

(b) Same results were not observed with a salt solution. Explain. 

(c) Can you suggest two more solutions which would show the same effect as shown by the milk solution?

Answer 1

(a) Milk is a colloid and would show Tyndall effect. 

(b) Salt solution is a true solution and would not scatter light. 

(c) Detergent solution, sulphur solution.