In biprism experiment, $$6^{\text {th }}$$ bright band with wavelength '$$\lambda_1$$' coincides with $$7^{\text {th }}$$ dark band with wavelength '$$\lambda_2$$' then the ratio $$\lambda_1: \lambda_2$$ is (other setting remains the same)

The time period of a satellite of earth is 5 hours. If the separation between the earth and the satellite will satellite is increased to four times the previous value, the new time period of the satellite will be

In the given circuit, the current in 8$$\Omega$$ resistance is 1.5 A. The total current (I) flowing in the circuit is

'Circle of least confusion' refers to which one of the following defects occurring in images formed by mirrors or lenses?