Modern Physics Lecture 5

Atomic line spectra can be observed when light passes through _____.

• a prism
• a diffraction grating
• none of these

• either a prism or a diffraction grating

Which statements are true about Millikan's experiment?

• It measured the mass to charge ratio of electrons.

• It measured the charge of electrons.

• It used charged oil droplets.

• It used magnetic field to deflect cathode rays.

Which statements are true about Planck's radiation law?

• The total radiated power is proportional to T⁴.

• The total radiated power is infinite.

• It is based on the assumption that energy is quantized.

• The wavelength where maximal power is radiated is proportional to 1/T.

The photoelectric effect contradicts classical physics because ____.

• the maximal kinetic energy of the emmitted electrons doesn't depend on the light intensity

• electrons are only emmited above a threshold frequency

• discrete charges are impossible in classical electrodynamics

• classical theory doesn't allow electrons to escape matter

Which statements are true about the Compton effect?

• It describes elastic scattering of photons on electrons.

• It can only be explained using relativistic mechanics.

• It is built on the assumption that light behaves like particles.

• It predicts that the scattered photons will have a shorter wavelenght.