The emissivities of the surfaces of two spheres P and Q of radii \(2R\) and \(3R\) are 0.35 and 0.7 respectively. The ratio of the powers radiated by the spheres P and Q is \(9:8\). If the wavelength at which sphere P emits radiations of maximum intensity is \(4000\ \text{\AA}\), then the wavelength at which sphere Q emits radiations of maximum intensity is:
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Use Stefan's law to find temperature ratio and then apply Wien's displacement law.