A compound microscope consists of an objective lens of focal length $1 \mathrm{cm}$ and an eye piece of focal length $5 \mathrm{cm}$ with a separation of $10 \mathrm{cm}.$ The distance between an object and the objective lens, at which the strain on the eye is minimum is $\frac{\mathrm{n}}{40}\mathrm{cm}.$ The value of $\mathrm{n}$ is.......