Consider electrons accelerated to a total energy of 20.0 GeV in the 3.00-km-long Stanford Linear Accelerator. How long does the accelerator appear to the electrons? Electron mass energy: 0.511 MeV.

Protons in an accelerator at the Fermi National Laboratory near Chicago are accelerated to a total energy that is 400 times their rest energy. What is the speed of these protons in terms of c?

A magnifier is rated at $2.5\times$ for a normal eye focusing on an image at the near point. (a) What is its focal length? (b) What is its focal length if the $2.5\times$ refer to a relaxed eye?

Calculate the energy, in electron volts, of a photon whose frequency is 620 THz,

Calculate the energy in electron volts of a photon having a wavelength in the x-ray range, 5.00 nm.

The diameters of the main rotor and tail rotor of a single-engine helicopter are 7.60 m and 1.02 m, respectively. The respective rotational speeds are 450 rev/min and 4 138 rev/min. Calculate the speeds of the tips of both rotors. Compare these speeds with the speed of sound, 343 m/s.

If the average energy released in a fission event is 208 MeV, find the total number of fission events required to operate a 100-W lightbulb for 1.0 h.

What is the surface temperature of Betelgeuse, a red giant star in the constellation of Orion, which radiates with a peak wavelength of about 970 nm?

A hydrogen atom initially in its ground state (n = 1) absorbs a photon and ends up in the state for which n = 3. (a) What is the energy of the absorbed photon? (b) If the atom returns to the ground state, what photon energies could the atom emit?

Tritium has a half-life of 12.33 years. What fraction of the nuclei in a tritium sample will remain after 5.00 yr? Discuss whether that is realistic.

A compass originally points north; at this location the horizontal component of the Earth’s magnetic field has a magnitude of $2 \times 10^-{5}$ T. A bar magnet is aligned east–west, pointing at the center of the compass. When the center of the magnet is 0.25 m from the center of the compass, the compass deflects $70^o$. What is the magnetic dipole moment of the bar magnet?

(i) Calculate the energy, in electron volts, of a photon whose frequency is (a) 620 THz, (b) 3.10 GHz, and (c) 46.0 MHz. (ii) Determine the corresponding wavelengths for the photons listed in part (i) and (iii) state the classification of each on the electromagnetic spectrum.

Earth's average surface temperature is about 287 K. Assuming Earth radiates as a blackbody, calculate $\lambda_{\max }$ for the Earth.