Assertion: Finest gold is red in colour. As the size of the particles increases, it appears purple then blue and finally gold. Reason: The colour of the colloidal solution depends upon the wavelength of the light scattered by the dispersed particles.

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KollegeApply · Accepted Answer

If both Assertion and Reason are correct and Reason is the correct explanation of the Assertion. Explanation: The finest gold colloidal solution is red because small gold particles scatter light that corresponds to longer wavelengths (red). As particle size increases, the scattering shifts, changing the color from purple to blue to finally gold. This color change is indeed due to the wavelength of light scattered by particles of different sizes in the colloidal solution, confirming that the reason correctly explains the assertion.

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