A spherical portion has been removed from a solid sphere having a charge distributed uniformly in its volume as shown in the figure. The electric field inside the emptied space is

Positive and negative point charges of equal magnitude are kept at $$\left(0,0, \frac{a}{2}\right)$$ and $$\left(0,0, \frac{-a}{2}\right)$$, respectively. The work done by the electric field when another positive point charge is moved from $$(-a, 0,0)$$ to $$(0, a, 0)$$ is

A magnetic field $$\overrightarrow{\mathrm{B}}=\mathrm{B}_{0} \hat{j}$$ exists in the region $$a < x < 2 a$$ and $$\overrightarrow{\mathrm{B}}=-\mathrm{B}_{0} \hat{j}$$, in the region $$2 a < x < 3 a$$, where $$\mathrm{B}_{0}$$ is a positive constant. A positive point charge moving with a velocity $$\vec{v}=v_{0} \hat{i}$$, where $$v_{0}$$ is a positive constant, enters the magnetic field at $$x=a$$. The trajectory of the charge in this region can be like,

Electrons with de-Broglie wavelength $$\lambda$$ fall on the target in an X-ray tube. The cut-off wavelength of the emitted X-rays is