$A$ laser beam is used for surgery because it can be...

The figure shows a schematic diagram of Young's Double Slit Experiment. If the distance $D$ between the slits and the screen is varied,choose the correct statement$(s)$.

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 $555 \,nm$.

Assertion: The colour of the green flower seen through red glass appears to be dark.
Reason: Red glass transmits only red light.

$A$ source emits light of wavelengths $4700 \ \mathring{A}$,$5400 \ \mathring{A}$,and $6500 \ \mathring{A}$. The light passes through red glass before being tested by a spectrometer. Which wavelength is seen in the spectrum?

Light from a point source falls on a small area placed perpendicular to the incident light. If the area is rotated about the incident light by an angle of $60^o$,by what fraction will the illuminance change?