What was removed by the sand filter?

A child wanted to separate the mixture of dyes constituting a sample of ink. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in figure. The filter paper was removed when the water moved near the top of the filter paper. (a) What would you expect to see, if the ink contains three different coloured components? (b) Name the technique used by the child. (c) Suggest one more application of this technique.

In Young's double slit experiment, one slit is covered with red filter and another slit is covered by green filter, then interference pattern will be

Light from a sources emitting two wavelengths lambda_(1) and lambda_(2) is allowed to fall on Young's double-slit apparatus after filtering one of the wavelengths. The position of interference maxima is noted. When the filter is removed both the wavelengths are incident and it is found that maximum intensity is produced where the fourth maxima occured previously. If the other wavelength if filtered, at the same location the third maxima is found. What is the raito of wavelength?

In a Young's double slit experiment, the source is white light. One of the holes is covered by a red filter and another by a blue filter. In this case

Explain why we cannot remove a filter paper from a funnel by blowing air into its narrow end.

How much is the filtering force required in the glomerulus? What is the nature of the filtrate in the PCT?