If a proton and anti-proton come close to each other and annihilate, how much energy will be released?

• 1.5 × 10^-10 J

• 3 × 10^-10 J

• 4.5 × 10^-10 J

• 2 ×  10^-10 J

A body at rest slides down a 30° inclined plane. The time taken by it to slide down is twice the time it takes when it slides down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is

• 0.43

• 0.37

• 0.64

• 0.75

An energy of 68.0 eV is required to excite a hydrogen-like atom in its second Bohr energy level to third energy level the charge of nucleus is Ze. The wavelength of a radiation required to eject the electron from first orbit to infinity is

• 2.2 nm

• 2.85 nm

• 3.2 nm

• 2.5 nm

Assertion:  Electrons in the atom are held due to Coulomb forces. 

Reason:  The atom is stable only because the centripetal force due to Coulomb's law is balanced by the centrifugal force.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Total energy of an electron in hydrogen atoms above 0 eV leads to

• ionisation of the atom

• accelerate the atom

• send the atom in higher excited state

• none of these

Ionisation potential of hydrogen atom is 13.6 V. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. The spectral lines emitted by hydrogen atoms according to Bohr's theory will be

• one

• two

• four

• three

137.

The current gain for a transistor working as common-base amplifier is 0.96. If the emitter current is 7.2 mA, then base current is

• 0.35 mA

• 0.28 mA

• 0.39 ma

• 0.43 mA

If the wavelength of 1line of Balmer series of hydrogen is 6561 A, the wavelength of the 2 line of series will be

• 9780 A^o

• 4860 A^o

• 8857 A^o

• 4429 A^o

A triply ionized beryllium ( Be³⁺ ) has the same orbital radius as the ground state of hydrogen. Then the quantum state n of Be³⁺ is

• n = 1

• n = 2

• n = 3

• n = 4

Ratio of longest wavelengths corresponding to Lyman and Balmer series in hydrogen spectrum is

• $\frac{7}{29}$

• $\frac{9}{31}$

• $\frac{5}{27}$

• $\frac{3}{23}$