When hydrogen atom is in its first excited level, its radius is [1997]

(1) four times, its ground state radius

(2) twice, its ground state radius

(3) same as its ground state radius

(4) half of its ground state radius

The ionisation potential of helium atom is 24.6 volt, the energy required to ionise it will be

(1) 24.6 eV            (2) 24.6 volt          (3) 13.6 volt                 (4) 13..6 eV

The ionisation energy of hydrogen atom is 13.6 eV, the ionisation energy of helium atom would be [1988]

(1) 13.6 eV            (2) 27.2 eV           (3) 6.8 eV            (4) 54.4 eV

If an electron in an hydrogen atom jumps from an orbit $n_i=3$ to an orbit with level $n_f=2$, the frequency of the emitted radiation is 

(1) $v=\frac{36 C}{5 R}$               (2) v = $\frac{CR}{6}$                (3) v = $\frac{5 RC}{36}$             (4) v  = $\frac{6 C}{R}$

The longest and shortest wavelength of the Lyman series are (respectively)

1.  $1215 \stackrel{0}{\mathrm{A}}, 500 \stackrel{0}{\mathrm{A}}$

2.  $1215 \stackrel{0}{\mathrm{A}}, 912 \stackrel{0}{\mathrm{A}}$

3.  $912 \stackrel{0}{\mathrm{A}}, 500 \stackrel{0}{\mathrm{A}}$

4. $912 \stackrel{0}{\mathrm{A}}, 700 \stackrel{0}{\mathrm{A}}$

The shortest wavelength of Balmer series is about 

1.  912$\stackrel{\mathrm{o}}{\mathrm{A}}$

2.  121$\stackrel{\mathrm{o}}{\mathrm{A}}$

3.  3648$\stackrel{\mathrm{o}}{\mathrm{A}}$

4.  4864$\stackrel{\mathrm{o}}{\mathrm{A}}$

Which of the following transition in a hydrogen atom will produce radiations of minimum wavelength?

1.  n = 2 to n = 1

2.  n = 5 to n = 3

3.  n = 10 to n = 5

4.  n = 10 to n = 3

The frequency Of radiation emitted during the transition of an electron from a second excited state to a first excited state in H-atom is ${\mathrm{f}}_0.$ The frequency of the same transition emitted by a singly ionized He ion is

1.  $2{\mathrm{f}}_0$

2.  $4{\mathrm{f}}_0$

3.  $\frac{{\mathrm{f}}_0}{2}$

4.  $\frac{{\mathrm{f}}_0}{4}$

When neutron moving with Kinetic Energy 2eV collides with 

stationary $H_1^1$ in the ground state, the collision will be:

1.  Must be elastic

2.  may be inelastic

3.  Both

4.  Must be perfectly inelastic

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

(1) $\frac{16}{25}\lambda$               

(2) $\frac{9}{16}\lambda$

(3) $\frac{20}{7}\lambda$               

(4) $\frac{20}{13}\lambda$