A two-slit experiment is run with red light of wavelength nm

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Quantum Mechanics · Origins of quantum theory

Quantum Mechanics: From the Photon to the Hydrogen Atom, Ch Light in lumps: blackbody radiation, the photoelectric effect and Compton scattering

Problem

A two-slit experiment is run with red light of wavelength

633

nm, and the distance from the source to the screen is

1.20

m. The beam is dimmed until photons leave the source, on average, one every

1000

crossing times. Take

c = 3.00\times10^{8}\ \mathrm{m\,s^{-1}}

hc = 1240

eV nm and

1

= 1.602\times10^{-19}

J. ((a)) How long does one photon take to cross the apparatus? ((b)) Find the beam power. ((c)) A camera builds up the fringe pattern from

1.0\times10^{7}

photons, every one of which reaches the screen. How long must the exposure last?