A laser pulse of duration 25 ms has a total energy of 1.4 J. If the wavelength of this radiation is 567 nm, how many photons are emitted in one pulse? (c = 3.00 108 m/s, h = 6.626 10-34 J s)
A) 4.8 1019 B) 3.2 1017 C) 9.9 1019 D) 4.0 1018 E) 1.6 1017
Question 2
A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle
A) is in the same direction as the particle's velocity.
B) causes the particle to slow down.
C) causes the particle to speed up.
D) is opposite the direction of the particle's velocity.
E) causes the particle to accelerate.