What is the ratio of the speed of an electron in the first orbit of an H-atom to the speed of light?

1.  $\frac{1}{137}$

2.  137

3.  $\frac{1}{83}$

4.  $\frac{1}{47}$

In the diagram shown below, two atomic transitions are shown. If ${\mathrm{\lambda }}_1$ $=$ $3000$ $\stackrel{\mathrm{o}}{\mathrm{A}}$ $\mathrm{and}$ ${\mathrm{\lambda }}_2$ $=$ $6000$ $\stackrel{\mathrm{o}}{\mathrm{A}},$ then the value of λ will be:

 
1.  2000 $\stackrel{\mathrm{o}}{\mathrm{A}}$

2.  4000 $\stackrel{\mathrm{o}}{\mathrm{A}}$

3.  4500 $\stackrel{\mathrm{o}}{\mathrm{A}}$

4.  9000 $\stackrel{\mathrm{o}}{\mathrm{A}}$

Let f₁ be the maximum frequency of the Lyman series, f₂ be the frequency of the first line of the Lyman series, and f₃ be the frequency of the series limit of the Balmer series, then which of the following is correct?

1.  $f_1$ - $f_2$ = $f_3$

2.  $f_2$ - $f_1$ = $f_3$

3.  $f_1$ + $f_2$ = $f_3$

4.  2$f_1$ = $f_2$ + $f_3$

If the wavelength of the first line in the Balmer Series of the hydrogen spectrum is λ, then what is the wavelength of the second line in this series?

1.  $\frac{20}{27}\lambda$

2.  $\frac{27}{20}\lambda$

3.  $\frac{25}{27}\lambda$

4.  $\frac{27}{25}\lambda$

In an atom, if the transition from n = 4 to n = 3 gives ultraviolet radiation, then to obtain infrared radiation, the transition should be:

Let R represent the orbital radius of an electron moving in an orbit and K represent its kinetic energy. Then the quantity KR varies with principal quantum number n as:

1.		2.
3.		4.

In an $\alpha$-particle scattering experiment, the number of particles scattered per minute in a direction perpendicular to the direction of incident particles is 40. What will be the number of particles scattered at an angle of 60° per minute?

The de-Broglie wavelength of an electron in the second orbit of a hydrogen atom is equal to:

What happens when an electron makes a transition from an excited state to the ground state of a hydrogen-like atom or ion?

A hydrogen atom is excited from the ground state to the state of principal quantum number 4. Then the number of spectral lines observed will be:

1. 3                   

2. 6

3. 5                   

4. 2