The relative luminosity of wavelength 600 nm is 0.6. Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555 nm.

Answer

B

Explanation

Relaive luminousity
Luminous flux of a source of
`=(given wavelength)/(Luminous flux of a source of)
55 nm of same poerre
`:.` Let the radiant flux needed by P watt
So, `0.6=(Luminous flux of source P watt)/(684P)`
`rarr Luminous flux of teh source (685P)x0.6=120x685`
`rarr P=120/0.6=200W