The spectrum obtained from a sodium vapour lamp is an example of

1. band spectrum

2.  continuous spectrum

3. emission spectrum

4. absorption spectrum

The radius of a hydrogen atom in its ground state is 5.3×10^-11 m. After collision with an electron, it is found to have a radius of 21.2 ×10^-11 m. What is the principal quantum number n of the final state of the atom?

1. n = 4 

2. n = 2 

3. n = 16 

4. n = 3

In terms of Bohr radius $a_0$, the radius of the second Bohr orbit of a hydrogen atom is given by [1992]

1. 4$a_0$ 

2. 8$a_0$ 

3. $\sqrt{2}$$a_0$     

4. 2$a_0$

 An x-ray tube is operating at 30 kV then the minimum wavelength of the x-rays coming out of the tube is:

1. 1.24 $\stackrel{0}{A}$

2. 0.413 $\stackrel{0}{A}$ 

3. 0.124 $\stackrel{0}{A}$ 

4. 0.13 $\stackrel{0}{A}$

A diatomic molecule is made of two masses $m_1 and m_2$ which are separated by a distance r.  If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by (n is an integer):

1. $\frac{{\left(m_1+m_2\right)}^2{n}^2{h}^2}{2m_1^2{m}_2^2{r}^2}$     

2. $\frac{n^2{h}^2}{2{\mathrm{\pi }}^2(m_1^{}+m_2^{})r^2}$

3. $\frac{2n^2{h}^2}{(m_1^{}+m_2^{})r^2}$   

4. $\frac{\left(m_1+m_2\right)n^2{h}^2}{8{\mathrm{\pi }}^2{m}_1^{}{m}_2^{}{r}^2}$

In a hydrogen atom, which of the following electronic transitions would involve the maximum energy change?

The Bohr model of the atom:

1. Assumes that the angular momentum of electrons is quantized

2. Uses Einstein's photoelectric equation

3. Predicts continuous emission spectra for atoms

4. Predicts the same emission spectra for all types of atoms

When a hydrogen atom is raised from the ground state to excited state

1. both KE and PE increase

2. both KE and PE decrease

3. PE increases and KE decreases

4. PE decreases and KE increases

The extreme wavelengths of Paschen series are

1. 0.365 $\mu m$ and 0.565 $\mu m$

2. 0.818 $\mu m$ and 0.189 $\mu m$

3. 1.45 $\mu m$ and 4.04 $\mu m$

4. 2.27 $\mu m$ and 7.43 $\mu m$

A hydrogen atom is in an excited state of principal quantum number (n). It emits a photon of wavelength ($\lambda$) when it returns to the ground state. The value of n is:

1. $\sqrt{\frac{\lambda R}{\lambda R-1}}$ 

2. $\sqrt{\frac{(\lambda R-1)}{\lambda R}}$

3. $\sqrt{\lambda (R-1)}$ 

4. None of these