The minimum wavelength of $$X$$-rays produced by an electron accelerated through a potential difference of $$V$$ volts is proportional to :
A $$12 \mathrm{~V}, 60 \mathrm{~W}$$ lamp is connected to the secondary of a step down transformer, whose primary is connected to ac mains of $$220 \mathrm{~V}$$. Assuming the transformer to be ideal, what is the current in the primary winding ?
Light travels a distance $$\mathrm{x}$$ in time $$t_{1}$$ in air and $$10 \mathrm{x}$$ in time $$t_{2}$$ in another denser medium. What is the critical angle for this medium?
A metal wire has mass $$(0.4 \pm 0.002) ~\mathrm{g}$$, radius $$(0.3 \pm 0.001) ~\mathrm{mm}$$ and length $$(5 \pm 0.02) ~\mathrm{cm}$$. The maximum possible percentage error in the measurement of density will nearly be :