The wavelength of the second line of Balmer series is 486.4 nm. What is the wavelength of the first line of Lyman series?
A bat emitting an ultrasonic wave of frequency 4.5 $$\times$$ 104 Hz at speed of 6 m/s between two parallel walls. The two frequencies heard by the bat will be
A disc of moment of inertia 4 kg - m$$^2$$ revolving with 16 rad/s is placed on another disc of moment of inertia 8 kg - m$$^2$$ revolving 4 rad/s. The angular frequency of composite disc
An electric current $I$ enters and leaves a uniform circular wire of radius $r$ through diametrically opposite points. A charged particle $$q$$ moves along the axis of circular wire passes through its centre with speed $$v$$. The magnetic force on the particle when it passes through the centre has a magnitude