Students are looking at trails in a cloud chamber and observe that suddenly trails appear, seemingly from nothing. They cannot explain this since matter cannot be created.
Which of the following statements explains the appearance of particles?
Larger particles were shielding the original particles so that they could not be seen until that position.
A photon spontaneously creates a particle and an antiparticle when its energy is converted to mass.
The particles were there all the time, but they were too small to be seen until this moment. As they move through the cloud chamber, they grow like a snowball rolling down a hill until they are large enough to leave a trail.
Two positrons were created from energy in the cloud and the tracks are visible.