Assessment: Modern Physics

What did the study of cathode rays directly lead to the discovery of?

What key observation about the photoelectric effect could NOT be explained by treating light as a pure wave?

What is the same, and what differs, between isotopes of the same element?

Find the energy of an electron in the n=4 level of hydrogen using Eₙ = −13.6/n² eV.

Find the recession speed of a galaxy 150 Mpc away, using H₀ ≈ 70 km/s/Mpc.

Light of frequency 6 × 10¹⁴ Hz strikes a metal with work function 1.5 eV. Find the maximum kinetic energy of ejected electrons, in eV (h = 6.63×10⁻³⁴ J·s, 1 eV = 1.6×10⁻¹⁹ J).

An electron drops from n=2 (E=−3.4 eV) to n=1 (E=−13.6 eV). Find the energy of the emitted photon.

Why do bones appear bright/white on a standard medical X-ray image?

How does carbon dating use isotopes to estimate the age of ancient remains?

What does Hubble's law imply about the origin of the universe?