A convex lens makes light rays converge (come together) at the focal point or focus. The distance from the center of the lens to the focal point is the focal length of the lens. Convex lenses are used in things like telescopes and binoculars to bring distant light rays to a focus in your eyes.
I would love to help; where’s the picture?
Answer:
E = 1.711 MeV
Explanation:
From the law of the conservation of energy:

where,
the kinetic energy of positron and electron = 1.2 MeV
Rest energy of the electron and the positron = 0.511 MeV
E = Energy of Photon = ?
Therefore,

<u>E = 1.711 MeV</u>
The best answer would be C.
The mass of an element depends on the number of particles found in the nucleus of the atom. Atomic mass can be computed by adding the number of protons and the number of neutrons. Protons and neutrons are found in the nucleus of an atom. So the answer must be letter C.