Incident light of wavelength $$\lambda=800 \mathrm{~nm}$$ produces a diffraction pattern on a screen $$1.5 \mathrm{~m}$$ away when it passes through a single slit of width $$0.5 \mathrm{~mm}$$. The distance between the first dark fringes on either side of the central bright fringe is
A transformer of $$100 \%$$ efficiency has 200 turns in the primary and 40000 turns in the secondary. It is connected to a $$220 \mathrm{~V}$$ main supply and secondary feeds to a $$100 \mathrm{~K} \Omega$$ resistance. The potential difference per turn is
Action and reaction can never balance out because
The current in a coil changes steadily from $$3 \mathrm{~A}$$ to $$5 \mathrm{~A}$$ in $$0.2 \mathrm{~s}$$ when an emf of $$2 \mu \mathrm{V}$$ is induced in it. The self-inductance of the coil is