Size and energy in the ground state of hydrogen atom

A Balmer series spectrum is formed when electrons from excited state fall down to ground state of n= ___.

In 1897, J J Thomson discovered the electron. This led him to propose the ____-pudding model of the atom.

The angular momentum (L) of an electron moving in a stable orbit around nucleus is

• Integral multiple of h

• Half integral multiple of h

When an electron moves from n=4 to n=1, what wavelength of energy is emitted?

• 97 nm

• 410 nm

• 434 nm

• 1282 nm

An atom has a mass number of 23 and atomic number 11. The number of protons is _________.

• 11

• 12

• 23

• 44

A copper wire has a diameter of 0.5 mm and resistivity of 1.68 X 10^-3 Ωm. What will be the length of this wire to make its resistance of 2Ω.

• 23.3m

• 20.3m

• 25.3m

• 30.3m

Which one of the following represents forward biasdiode?

• 
• 
• 
• 

The tunnelling through a potential barrier increases if

• Hight and width of the barrier increased

• Height and width of the barrier reduced

• Height increased and width reduced of the barrier

• Height reduced and width increased of the barrier

If a small amount of antimony is added to germanium crystal

• it becomes a p-type semiconductor

• the antimony becomes an acceptor atom

• there will be more free electrons than holes in the semiconductor

• its resistance is increased

Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is

• 0.75A

• 0A

• 0.25A

• 0.5 A