51.

The principle of LASER action involves

• amplification of particular frequency emitted by the system

• population inversion

• stimulated emission

• All ofthe above

Solar spectrum is an example for

• line emission spectrum

• continuous emission spectrum

• band absorption spectrum

• line absorption spectrum

The ratio of minimum wavelengths of Lyman and Balmer series will be

• 1.25

• 0.25

• 5

• 10

Hydrogen atom does not emit X-rays because

• it contains only a single electron

• energy levels in it are far apart

• its size is very small

• energy levels in it are very close to each other

In the Bohr model of hydrogen atom, the electron is pictured to rotate in a circular orbit of radius 5 x 10^-11 m at a speed 2.2 × 10⁶ m/s. What is the current associated with electron motion ?

• 1.12 mA

• 3 mA

• 0.75 mA

• 2.25 mA

If an electron and a proton have the same de-Broglie wavelength, then the kinetic energy of the electron is

• zero

• less than that of a proton

• more than that of a proton

• equal to that of a proton

In ruby laser, the stimulated emission is due to transition from

• metastable state to any lower state

• any higher state to lower state

• metastable state to ground state

• any higher state to ground state

The kinetic energy of an electron gets tripled, then the,de-Broglie wavelength associated with it changes by a factor

• $\frac{1}{3}$

• $\sqrt{3}$

• $\frac{1}{\sqrt{3}}$

• 3

The spectral series of the hydrogen atom that lies in the visible region of the electromagnetic spectrum

• Paschen

• Balmer

• Lyman

• Brackett

According to the quark model, it is possible to build all the hadrons using

• 2 quarks and 3 antiquarks

• 3 quarks and 2 antiquarks

• 3 quarks and 3 antiquarks

• 2 quarks and 2 antiquarks