A proton and alpha particle are accelerated through the same potential difference. The ratio of the de-Broglie wavelength of proton to that of alpha particle will be (mass of alpha particle is four times mass of proton.)

Two rods of same length and material are joined end to end. They transfer heat in 8 second. When they are joined in parallel they transfer same amount of heat in same conditions in time

A pendulum clock is running fast. To correct its time, we should

A pipe closed at one end has length $$0.8 \mathrm{~m}$$. At its open end $$0.5 \mathrm{~m}$$ long uniform string is vibrating in its $$2^{\text {nd }}$$ harmonic and it resonates with the fundamental frequency of the pipe. If the tension in the wire is $$50 \mathrm{~N}$$ and the speed of sound is $$320 \mathrm{~m} / \mathrm{s}$$, the mass of the string is