Three light sources A, B and C emit equal amount of radiant energ… - Vidyadip

Question

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

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

✓

Answer

X_B > X_A, X_B > X_C

Explanation:

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

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

$\therefore$ 555 - 450 = 105

But 700 - 555 = 145

So, X_A's brightness will be greater than that of X_C_.

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