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In a filament bulb the energy is first used to heat the filament to a high temperature wasting the energy while the mercury vapour using lesser energy to give out light therefore the efficeny is better
1)why is luminous efficiency small for a filament bulb as compared to a mercury varour lamp?
2)the yellow colour has greater luminous efficieny as compared to the other colours Can we increase the illuminating power of a white light source by putting a yellow plastic paper around this source
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