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Photometry — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsPhotometry1 Mark
Question
The one parameter that determines the brightness of a light source sensed by an eye is:
  1. Energy of light entering the eye per second.
  2. Wavelength of the light.
  3. Total radiant flux entering the eye.
  4. Total luminous flux entering the eye.
✓

Answer

  1. Total luminous flux entering the eye.
Explanation:

Total luminous flux is the total brightness producing capability of a radiating source. Or, it is the measurement of the total energy entering our eyes that produces the sensation of vision.
  1. This cannot be the correct answer because all energies cannot be sensed by our eyes.
  2. This cannot be the correct answer because all wavelengths do not produce any sensation in our eyes.
  3. This cannot be the correct answer because all wavelengths contributing the radiant flux are not always visible to our eyes. There may be a large radiant flux yet there may not be any sensation of vision.

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