What is the frequency of the light emitted from a sodium lamp?

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 $555 \,nm$.

$A$ laser beam is used for carrying out surgery because it

The maximum illumination on a screen at a distance of $2\, m$ from a lamp is $25\, lux.$ The value of total luminous flux emitted by the lamp is

Statement $(S)$: Using Huygen's eye-piece,measurements can be taken but are not correct.
Reason $(R)$: The cross wires,scale,and final image are not magnified proportionately because the image of the object is magnified by two lenses,whereas the cross-wire scale is magnified by one lens only.
Identify the correct option from the following:

Fraunhofer lines are produced by the absorption of light in