Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12

# 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. - Physics

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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 XA, XB and XC respectively. Then, ________ .

#### Options

• XA > XB, XC > XB

• XA > XB, XB > XC

• XB > XA, XB > XC

• XB > XA, XC > XB

#### Solution

XB > XA, XB > XC

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

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

∴ 555 - 450 = 105

But 700 - 555 = 145

So, XA's brightness will be greater than that of XC.

Concept: Light Process and Photometry
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#### APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 1
Chapter 22 Photometry
MCQ | Q 2 | Page 454
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