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MCQ

Fill in the Blanks

Three light sources A, B and C emit equal amount of radiant energy per unit time. The wavelengths emitted by the three source are 450 nm, 555 nm and 700 nm respectively. The brightness sensed by an eye for the sources are X_{A}, X_{B} and X_{C} respectively. Then, ________ .

#### Options

X

_{A}> X_{B}, X_{C}_{ }> X_{B}X

_{A}> X_{B}, X_{B}> X_{C}X

_{B}> X_{A}, X_{B}_{ }> X_{C}X

_{B}> X_{A}, X_{C}_{ }> X_{B}

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#### Solution

X_{B} > X_{A}, X_{B}_{ }> X_{C}

Wavelength of light B is 555 nm. It has the highest luminosity; hence, X_{B} will be highest.

Again, 450 nm is nearer to 555 nm than 700 nm.

∴ 555 - 450 = 105

But 700 - 555 = 145

So, X_{A}'s brightness will be greater than that of X_{C}_{.}

Concept: Light Process and Photometry

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