In Bohr's model if the atomic radius of the first orbit is r₀, then what will be the radius of the third orbit?
1. $\frac{{\mathrm{r}}_0}{9}$              

2. ${\mathrm{r}}_0$
3. $9{\mathrm{r}}_0$               

4. $3{\mathrm{r}}_0$

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.  $\frac{1}{47}$

The total energy of an electron in the first excited state of a hydrogen atom is about –3.4 eV. Its kinetic energy in this state will be:

1. –6.8 eV

2. 3.4 eV

3. 6.8 eV

4. –3.4 eV

In the n^th orbit, the energy of an electron is \(\mathrm{E}_{\mathrm{n}}=-\frac{13.6}{\mathrm{n}^2} \mathrm{~eV}\) for the hydrogen atom. What will be the energy required to take the electron from the first orbit to the second orbit?

1. 10.2 eV

2. 12.1 eV 

3. 13.6 eV

4. 3.4 eV 

If an electron in a hydrogen atom jumps from the 3rd orbit to the 2nd orbit, it emits a photon of wavelength $\lambda$. What will be the corresponding wavelength of the photon when it jumps from the 4^th orbit to the 3rd orbit?

1. $\frac{16}{25}\lambda$               

2. $\frac{9}{16}\lambda$

3. $\frac{20}{7}\lambda$               

4. $\frac{20}{13}\lambda$

Hydrogen ₁H¹, Deuterium ₁H², singly ionised helium (₂He⁴)⁺, and doubly ionised lithium (₃Li⁶)⁺⁺ all have one electron around the nucleus. Consider an electron transition from n = 2 to n = 1. If the wavelengths of emitted radiations are λ₁ ,λ₂ ,λ₃ and  λ₄ respectively, then approximately which one of the following is correct?

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

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 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

The ionisation energy of a hydrogen atom is 13.6 eV. Following Bohr's theory, what is the energy corresponding to a transition between the 3^rd and 4^th orbit?
1. 3.40 eV
2. 1.51 eV
3. 0.85 eV 
4. 0.66 eV