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/tumblerin the box as shown in the Figure. 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?

A group of students took an old shoe box and covered it with a black p

1.	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/tumblerin the box as shown in the Figure. 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» Solution :(a) MILK sample is a colloidal sol also called emulsion. It got ILLUMINATED because of the scattering of light on passing through it. The phenomenon is known as Tyndall effect. (b) The SALT solution is a true solution and not a colloidal solution. It will not show any Tyndall effect. (c ) A solution of sulphur in WATER and a solution of STARCH in water.