In the given figure, $$C$$ is middle point of line $$S_1 S_2$$. A monochromatic light of wavelength $$\lambda$$ is incident on slits. The ratio of intensities of $$S_3$$ and $$S_4$$ is
A simple telescope, consisting of an objective of focal length $$60 \mathrm{~cm}$$ and a single eye lens of focal length $$5 \mathrm{~cm}$$ is focused on a distant object in such a way that parallel rays emerge from the eye lens. If the object subtends an angle of $$2^{\circ}$$ at the objective, the angular width of the image is
A specimen of silicon is to be made $$P$$-type semiconductor for this one atom of indium, on an average, is doped in $$5 \times 10^7$$ silicon atoms. If the number density of silicon is $$5 \times 10^{22}$$ atom/$$\mathrm{m}^3$$ then the number of acceptor atoms per $$\mathrm{cm}^3$$ will be
The angle of dip, if dip needle oscillating in vertical plane makes 40 oscillations per min in a magnetic meridian and 30 oscillations per minute in vertical plane at right angle to the magnetic meridian is