The size of the nucleus is of the order of

$A$ certain particle carries $2.5 \times 10^{-16} \, C$ of static electric charge. Calculate the number of electrons present in it.

The nucleus and an atom can be assumed to be spherical. The radius of the nucleus of mass number $A$ is given by $R_n = 1.25 \times 10^{-13} \times A^{1/3} \, \text{cm}$. The atomic radius is $1 \, \mathring{A}$. If the mass number is $64$,the fraction of the atomic volume that is occupied by the nucleus is:

Which of the following statements is correct about the cathode rays?
$1$. These rays start from anode and move towards cathode.
$2$. They are visible with human eye.
$3$. In presence of electric and magnetic fields,they behave like positively charged particles.
$4$. Their characteristic does not depend on the nature of material at electrode.

The fact that the atom is divisible was determined from ............ .

What is the ratio of the mass of an electron to the mass of a proton?