When the atoms of gold sheet are bombarded with a beam of $\alpha$ -particles, only a few a-particles get deflected where as most of them go straight undeflected. This is because:

1.	The force of attraction on the $\alpha$-particles by the oppositely charged electron is not sufficient.
2.	The nucleus occupies much smaller volume as compared to the volume of atom.
3.	The force of repulsion on fast moving $\alpha$-particles is very small.
4.	The neutrons in the nucleus do not have any effect on $\alpha$-particles.

Using radiation of wavelength 3500 Å, it is observed that the maximum kinetic energy of the emitted photoelectrons is 1.6 eV for potassium. Calculate the work function of the metal. [h=6.626 x 10^-34 Js, 1 eV=1.6 x 10^-19 J]

1. 3 eV

2. 2.5 eV

3. 3.5 eV

4. 2 eV

To give designation to an orbital, we need

1. Principal and azimuthal quantum number

2. Principal and magnetic quantum number

3. Azimuthal and magnetic quantum number

4. Principal, azimuthal and magnetic quantum numbers.

The rest mass of a proton is 1.673 x 10^-27 kg and that of the electron is 9.109 x 10^-31 kg. What must be the speed of the proton which has the same de Broglie wavelength as an electron moving with a speed of 9 x 10⁶ m/s?

1. 3600 m/s

2. 4900 m/s

3. 4300 m/s

4. 5600 m/s

Which one of the following statement is not true about the quantum numbers n, l, m and s

1. m gives the information on the energy of the electron in a given orbital.

2. l gives an idea of the shape of the orbital.

3. n gives information on the size of the orbit.

4. s gives the direction of spin of the electron in the orbital.

The number of electrons in the valence shell of calcium is 

1. 6

2. 8

3. 2

4. 4

The brackett series of spectral lines arise when an electron in an excited hydrogen atom jumps from an energy level

1. n=5 to n=1

2. n=5 to n=3

3. n=5 to n=4

4. n=5 to n=2

What is the ratio of the time period of revolution of electron He⁺ ion sample in the orbit where the path length is three time the de-broglies wavelength to the time period of revolution in the ground state –

1. 27:1

2. 1:27

3. 9:8

4. 8:9

The ratio of the wavelengths of the last lines of the Balmer and Lyman series is:

1. 4:1

2. 27:5

3. 3:1

4. 9:4

The energy of the emitted photon when an electron in $B{e}^{3+}$ ion returns from n=2 level to the ground state is 

1. 2.616 x 10^-17J

2. 26.16 x 10^-17J

3. 261.6 x 10^-18J

4. 2616 x 10^-17J