Let "m" represent the mass of an electron, and "c" represent the speed of light. In order to create an electron-positron pair, we must start with a photon whose energy is
A) at least mc2.
B) at least 2mc2.
C) at least 4mc2.
D) any value greater than zero.
E) Actually it is impossible to create such pairs from photons.
B
You might also like to view...
An X-ray burster occurs in a pulsar when ____
a. accreted helium suddenly fuses in a nova-like explosion b. the Chandrasekhar limit is exceeded and the object collapses c. carbon deflagration destroys the object d. it merges with a binary companion e. hydrogen fusion ignites in an accretion disk around it
Why did Galileo's observations of moons orbiting Jupiter disagree with geocentric model of the universe of his time?
a. The moons moved in non-circular orbits about Jupiter. b. The moons did not appear to orbit the Sun. c. The moons did not appear to orbit Earth. d. The moons appeared to be too small, and therefore too far away, to be considered part of the solar system.
Two concentric conducting spheres of radii a = 5 cm and b = 10 cm have a potential difference V = 100 V between them. What is the charge carried by each sphere?
A) 100 nC B) 5.5 nC C) 1.1 nC D) 10 nC E) 2.2 nC
The position of a mass that is oscillating on a spring is given by x = (12.3 cm) cos[(1.26 s-1)t]. What is the speed of the mass when t = 0.805 s?
A) - 13.2 cm/s B) 13.2 cm/s C) 8.19 cm/s D) - 8.19 cm/s E) 0 cm/s