The de-Broglie wavelength of a proton and $$\alpha$$-particle are equal. The ratio of their velocities is :

According to Bohr atomic model, in which of the following transitions will the frequency be maximum?

A uniform metallic wire is elongated by 0.04 m when subjected to a linear force F. The elongation, if its length and diameter is doubled and subjected to the same force will be ________ cm.

An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2.25 from vacuum. The wavelength of this wave in that medium will be _________ $$\times$$ 10^$$-$$2 cm.