The heaviest particle among the following is:

The masses of an electron,a proton and a neutron respectively will be in the ratio

Which of the following particles cannot be accelerated by an electric or magnetic field?

Fill in the blanks:
$(i)$ $R. A. Millikan$ developed the ......... method to determine the charge of an electron.
$(ii)$ The positively charged particles in a modified cathode ray tube are called ............ .
$(iii)$ The smallest and lightest positive ion obtained from hydrogen is ........... .
$(iv)$ In the year $1932$,$Chadwick$ discovered ........... .

Cathode rays have

The number of electrons in the nucleus of $^{12}C$ is