## Focus 1 1.31 Atoms

derinceltik1K
Posts: 51
Joined: Sat Aug 17, 2019 12:15 am

### Focus 1 1.31 Atoms

1.31 In a recent suspense film, two secret agents must penetrate a criminal's stronghold monitored by a lithium photomultiplier cell that is continually bathed in light from a laser. If the beam of light is broken, an alarm sounds. The agents want to use a hand- held laser to illuminate the cell while they pass in front of it. They have two lasers, a high-intensity red ruby laser (694 nm) and a low-intensity violet GaN laser (405 nm), but they disagree on which one would be better. Determine
(a) which laser they should use
(b) the kinetic energy of the electrons emitted. The work function of lithium is 2.93 eV.

Are these questions included in the syllabus ?
How would we solve this?

Simon Dionson 4I
Posts: 107
Joined: Sat Sep 14, 2019 12:17 am

### Re: Focus 1 1.31 Atoms

Use E = hc/lambda to find the individual energies of the lasers. Convert the work function from eV to joules. Choose the laser that is greater the work function and from there you have the laser and can calculate the kinetic energy from E = (work function) - (kinetic energy).