It is now believed that protons and neutrons (which consitude nuclel of ordinary matter) are themselves built out of more elementary units called quarks. A proton and a neutron consits os three quarks each. Two types of quarks , the so called 'up' quark, (denoted by U) of charge `+ (2//3)` e and the 'down' quark (denoted by d) of charge `(-1//3)` e together with electrons build up ordinary matter. (Quarks of each other types have also been found which give rise to different unsual varieties of matter). Suggest a possible quark composition of a proton and neutron.

Explanation

In a proton, suppose there aer n up quarks
`:.` no. of down quarks = `(3-n)`
Total charge on proton : `((2)/(3) e)n + (-(1)/(3) e) (3-n) = +e`
`(2)/(3)en - e + (n e)/(3) = e` `ne((2)/(3) + (1)/(3)) = 2e` `n e = 2e` `n = 2`
`:.` No of up quarks = 2, No fo down quarks `= 3-2 = 1 :.` A proton may be represted as `p implies UUd`
In a neutron, again suppose, no. of marks = n
`:.` no of down quarks = `(3-n)`
Total charge on neutron : `((2)/(3)e)n - (1)/(3) en = 0 en = e, n = 1`
`:.` No. of up quarks = 1 No of down quarks `= 3-1 = 2`
`:.` A neutron can be represented as `n implies U dd`