Question 7 :
The atomic weight of an element is $23$ and its atomic number is $11$. The number of proton, electrons and neutrons respectively, present in the atom of the element are

Question 9 :
In an oil drop experiment, the following charges (in arbitary units) were found on a series of oil droplets:<br/>2.30 $\times$ 10$^{-15}$, 6.90 $\times$ 10$^{-15}$, 1.38 $\times$ 10$^{-14}$<br/>5.75 $\times$ 10$^{-15}$, 3.45 $\times$ 10$^{-15}$, 1.96 $\times$ 10$^{-14}$<br/>The magnitude of charge on the electron (in the same unit) is:

Question 10 :
Match the column- I with Column - II and select the correct answer:<br/><table class="wysiwyg-table"><tbody><tr><td>Column - I</td><td>Column -II</td></tr><tr><td>(I) Curie</td><td>A. $10^6 \, dis \, sec^{-1}$</td></tr><tr><td>(II) Rutherford</td><td>B. $3.7 \times 10^{10} \, dis\, sec^{-1}$</td></tr><tr><td>(III) Becquerel</td><td>C. 1 dis $sec^{-1}$</td></tr></tbody></table>

Question 11 :
Among the following, the correct statement about cathode ray discharge tube is:&#160;

Question 12 :
Assertion: e/m ratio in case of anode ray experiment is different for different gases. Reason: The ion of gases formed after the ejection of electron are different if gas is different.

Question 14 :
The mass and charge of one mole of electrons, respectively is:

Question 15 :
Assertion: The characteristics of cathode rays do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube. Reason: Cathode rays consist of negatively charged particles, called electrons.

Question 18 :
If the mass of electron is doubled, the speed of electron revolving around $Li^{2+}$ nucleus will ________

Question 19 :
The oil drop experiment by R.A. Mulliken was performed to find :

Question 20 :
A beam of some kind of particle of velocity $2\times {10}^{7}m/s$ is scattered by a gold $(z=79)$ foil. Find specific charge of this particle (charge/mass) if the distance of closest approach is $7.9\times {10}^{-14}m$.