Questions from College Physics

Q: A 10 W laser emits a beam of light 4.0

A 10 W laser emits a beam of light 4.0 mm in diameter. The laser is aimed at the Moon. By the time it reaches the Moon, the beam has spread out to a diameter of 85 km. Ignoring absorption by the atmos...

Q: You take a homemade “accelerometer” to an amusement park.

You take a homemade “accelerometer” to an amusement park. This accelerometer consists of a metal nut attached to a string and connected to a protractor, as shown in...

Q: A light-emitting diode (LED) has the property that

A light-emitting diode (LED) has the property that electrons can be excited into the conduction band by the electrical energy from a battery; a photon is emitted when the electron drops back to the va...

Q: You are trying to communicate with a spaceship that is traveling at

You are trying to communicate with a spaceship that is traveling at 1.2 × 108 m/s away from Earth. If you send a message at a frequency of 55 kHz, to what frequency should the astronauts on the ship t...

Q: A photoconductor (see Conceptual Question 13) allows charge to flow

A photoconductor (see Conceptual Question 13) allows charge to flow freely when photons of wavelength 640 nm or less are incident on it. What is the band gap for this photoconductor?

Q: To measure the speed of light, Galileo and a colleague stood

To measure the speed of light, Galileo and a colleague stood on different mountains with covered lanterns. Galileo uncovered his lantern and his friend, seeing the light, uncovered his own lantern in...

Q: In a ruby laser, laser light of wavelength 694.3

In a ruby laser, laser light of wavelength 694.3 nm is emitted. The ruby crystal is 6.00 cm long, and the index of refraction of ruby is 1.75. Think of the light in the ruby crystal as a standing wave...

Q: What are the three lowest angular speeds for which the wheel in

What are the three lowest angular speeds for which the wheel in Fizeau’s apparatus (see Fig. 22.11) allows the reflected light to pass through to the observer? Assume the distance between the notched...

Q: A proton and a deuteron (which has the same charge as

A proton and a deuteron (which has the same charge as the proton but 2.0 times the mass) are incident on a barrier of thickness 10.0 fm and “height” 10.0 MeV. Each particle has a kinetic energy of 3.0...

Q: By expressing ϵ0 and μ0 in base SI units (kg,

By expressing ϵ0 and μ0 in base SI units (kg, m, s, A), show that the only combination of the two with dimensions of speed is (ϵ0μ0)−1/2.