List of top Physics Questions on de broglie hypothesis asked in WBJEE

The mass of an electron is \(9.1\times10^{-31}\ \text{kg}\). If its K.E. is \(3.0\times10^{-25}\ \text{J}\), its wavelength is (approximately):
The de-Broglie wavelength of an electron in 4th orbit is (where \( r \) = radius of the 1st orbit)
The de-Broglie wavelength of a moving bus with speed \( v \) is \( \lambda \). Some passengers left the bus at a stoppage. Now when the bus moves with twice of its initial speed, its kinetic energy is found to be twice its initial value. What is the de-Broglie wavelength of the bus now?
The de-Broglie wavelength of a moving bus with speed \( v \) is \( \lambda \). Some passengers left the bus at a stop. Now, when the bus moves with twice of its initial speed, its kinetic energy is found to be twice of its initial value. What is the de-Broglie wavelength of the bus now?