Two short magnets of equal dipole moments M are fastened perpendicularly at their centres as given in the figure. The magnitude of the magnetic filed at a distance d from the centre on the bisector of the right angle is 

1. $\frac{{\mu }_0}{4\pi }\frac{m}{d^3}$

2. $\frac{{\mu }_0}{4\pi }\frac{\sqrt{2}M}{d^3}$

3. $\frac{{\mu }_0}{4\pi }\frac{2\sqrt{2}M}{d^3}$

4.  $\frac{{\mu }_0}{4\pi }\frac{2M}{d^3}$

1. \( {K}_{eq}{=}\frac{{L}_{1}{+}{L}_{2}}{\frac{{L}_{1}}{{K}_{1}}{+}\frac{{L}_{2}}{{K}_{2}}}\)
2. \( {K}_{eq}{=}\frac{{L}_{1}{+}{L}_{2}}{{K}_{1}{K}_{2}}\)
3. \( {K}_{eq}{=}\frac{{L}_{1}}{{K}_{1}{+}{K}_{2}}{+}\frac{{L}_{2}}{{K}_{1}{+}{K}_{2}}\)
4. \( {K}_{eq}{=}\frac{{L}_{1}{L}_{2}}{{L}_{1}{+}{L}_{2}}\)

Photoelectric effect experiments are performed using three different metal plates \(p,q\) and \(r\) having work functions ${}_{}$\(Q_{p}=2\) eV, ${\mathrm{}}_{}$\(Q_{q}=2.5\) eV and ${}_{}$\(Q_{r}=3.0\) eV, respectively. A light beam containing wavelength of \(550\) nm, \(450\) nm and \(350\) nm with equal intensities illuminates each of the plates. The correct \((I\text-V)\) graph for the experiments is: $$(Take \(\text{hc}=1240~\text{eV-nm}\))

 

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