A Level Physics Practice Exam

What type of quark configurations are present in a neutron?

1. Up, Up, Down

2. Down, Down, Down

3. Up, Down, Down

4. Up, Up, Up

The correct answer is: Up, Down, Down

The neutron is a type of baryon, a subatomic particle made up of three quarks. In the case of a neutron, its specific quark configuration is one up quark and two down quarks. This combination gives the neutron its neutral charge, as the up quark carries a charge of +2/3, and each down quark carries a charge of -1/3. When you combine these charges (1 x +2/3 from the up quark and 2 x -1/3 from the down quarks), the overall charge sums to zero: \[ \frac{2}{3} + \left(-\frac{1}{3}\right) + \left(-\frac{1}{3}\right) = 0 \] This neutral charge is a defining characteristic of neutrons. The other configurations listed do not accurately reflect the quark composition of a neutron, as they either involve incorrect numbers of quark types or would result in particles with different properties, such as charge. Therefore, the correct answer, which identifies the correct configuration of one up quark and two down quarks, accurately describes the structure of a neutron.