In Young's double slit experiment, intensity of light at a point on the screen, where the path difference becomes $\lambda$ is $I$. The intensity at a point on the screen, where the path difference becomes $\frac{\lambda}{3}$ is

The diameter of the objective of a telescope is 3.6 m . The limit of resolution of the telescope for a light of wavelength 540 nm is

Young's double slit experiment is performed with monochromatic light of wavelength $6000 \mathring{A}$. If the intensity of light at a point on the screen, where path difference of $2000 \mathring{A}$ is $I_1$ and the intensity of light at a I point on the screen, where the path difference is $1000 \mathring{A}$ is $I_2$, then $I_1: I_2=$