What is the ratio of the circumference of the first Bohr orbit for the electron in the hydrogen atom to the de-Broglie wavelength of electrons having the same velocity as the electron in the first Bohr orbit of the hydrogen atom?

1. 1:1

2. 1:2

3. 1:4

4. 2:1

The difference between n^th and (n+1)^th Bohr's radius of the 'H' atom is equal to its (n - 1)^th Bohr's radius. What is the value of n?

1.  1

2.  2

3.  3

4.  4

What is the ratio of the energies of the hydrogen atom in its first and second excited states?

1. $\frac{1}{4}$

2. $\frac{4}{9}$

3. $\frac{9}{4}$

4. 4

Which of the following transitions gives a photon the maximum energy?

1. n = 1 to n = 2

2. n = 2 to n = 1

3. n = 2 to n = 6

4. n = 6 to n = 2

Whose atomic model describes electrons being embedded in a gel of positive charge?

The Rutherford $\mathrm{\alpha }$-particle experiment shows that most of the $\mathrm{\alpha }$-particles pass through almost unscattered while some are scattered through large angles. What information does it give about the structure of the atom?

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

How much is the total energy of an electron in the first orbit of a hydrogen atom equal to?

An electron revolves around a nucleus of charge Ze. In order to excite the electron from the state n=3 to n=4, the energy required is 66.0 eV. The value of Z will be:

1. 25 

2. 10

3. 4 

4. 5

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.  $\frac{1}{47}$