A charged particle moving in a uniform magnetic field and losses $$16 \%$$ of its kinetic energy. The radius of curvature of its path changes by
A thin but rigid semicircular wire frame of radius $$r$$ is hinged at $$O$$ and can rotate in its own vertical plane. A smooth peg $$P$$ starts from $$O$$ and moves horizontally with constant speed $$2 v_0$$ lifting the frame upward as shown in figure. Find the angular velocity $$\omega$$ of the frame when its diameter makes an angle of $$60^{\circ}$$ with vertical.
After two hours one-eight of the starting amount of a certain radioactive isotope remained undecayed. The half-life of the isotope is
A thin plano-convex lens of focal length $$f$$ is split into two halves one of the halves is shifted along the optical axis. The separation between object and image formed by one of the half-lenses is 2.4 and the magnification of same lens is 2. If $$f$$ and $$d$$ be the focal length of the lens and separation between the two halves respectively then