Lasers
Answers are for parents and teachers.
1
A photon has wavelength 775 nm. What is its energy? (hc = 1240 eV·nm)
1.6 eV
2
A pulse has energy 9 J and lasts 3 ms. What is the power in W?
3000
3
Divergence 2·10⁻³ rad, distance 250 m. What is the beam diameter?
0.5 m
4
Power 3 mW, beam cross-section 1 mm². What is the intensity?
3·10³ W/m²
5
Why does a laser need population inversion and a resonator?
Inversion makes stimulated emission outweigh absorption; the resonator passes the light back and forth, amplifying it and giving it direction.