The radius of the central zone of a circular zone plate is $2.3\,mm$. The wavelength of the incident light is $5893\,\mathring{A}$. The source is at a distance of $6\,m$. What is the distance of the first image in meters?

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 $555 \,nm$.

In interference and diffraction, the light energy is redistributed. If it reduces in one region, producing a dark fringe, it increases in another region, producing a bright fringe. Statement $A$: As there is no gain or loss of energy, these phenomena are consistent with the principle of conservation of energy. Statement $B$: Diffraction and interference are characteristics exhibited only by light waves. Choose the correct answer from the options given below:

$A$ white screen illuminated by green and red light appears to be

The intensity of light from a continuously emitting laser source operating at $638 \,nm$ wavelength is modulated at $1 \,GHz$. The modulation is done by momentarily cutting the intensity off with a frequency of $1 \,GHz$. What is the farthest distance apart two detectors can be placed in the line of the laser light,so that they can see the portions of the same pulse simultaneously?
(Consider the speed of light in air $c = 3 \times 10^{8} \,m/s$)

Red light differs from blue light in its