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 boxes shown in the given 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. Q.1 Explain why the milk sample was illuminated. Name the phenomenon involved.
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Here the sample milk was illuminated as it was a colloid due to the Tyndall effect.
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Answer:
1) Explain why the milk sample was illuminated ? Name the phenomenon involved.
➣ Milk is a colloid. If a beam of light is put on a milk sample contained in a beaker the path of light beam is illuminated and become visible when seen from the other side. This is because the colloidal particles are big enough to scatter light falling on them. This scattered light enters our eyes and we are able to see the path of light beam.
The scattering of light by colloidal particles is called Tyndall effect.
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