Problems

How many X-ray photons per second are created by an X-ray tube that produces a flux of X-rays having a power of 1.00 W? Assume the average energy per photon is 75.0 keV.

1. 8.33 × 10¹⁵ photons
2. 9.1 × 10⁷ photons
3. 9.1 × 10⁸ photons
4. 8.33 × 10¹³ photons

What is the frequency of a photon produced in a CRT using a 25.0-kV accelerating potential? This is similar to the layout as in older color television sets.

1. 6.04 × 10⁻⁴⁸ Hz
2. 2.77 × 10⁻⁴⁸ Hz
3. 3.02 × 10¹⁸ Hz
4. 6.04 × 10¹⁸ Hz

What is the binding energy in eV of electrons in magnesium, if the longest-wavelength photon that can eject electrons is 337 nm?

1. 7.44 × 10⁻¹⁹ J
2. 7.44 × 10⁻⁴⁹ J
3. 5.90 × 10⁻¹⁷ J
4. 5.90 × 10⁻¹⁹ J

Photoelectrons from a material with a binding energy of 2.71 eV are ejected by 420-nm photons. Once ejected, how long does it take these electrons to travel 2.50 cm to a detection device?

1. 8.5 × 10⁻⁶ s
2. 3.5 × 10⁻⁷ s
3. 43.5 × 10⁻⁹ s
4. 8.5 × 10⁻⁸ s

What is the momentum of a 0.0100-nm-wavelength photon that could detect details of an atom?

1. 6.626 × 10⁻²⁷ kg ⋅ m/s
2. 6.626 × 10⁻³² kg ⋅ m/s
3. 6.626 × 10⁻³⁴ kg ⋅ m/s
4. 6.626 × 10^-23 kg ⋅ m/s

The momentum of light is exactly reversed when reflected straight back from a mirror, assuming negligible recoil of the mirror. Thus the change in momentum is twice the initial photon momentum. Suppose light of intensity 1.00 kW/m2 reflectsfrom a mirror of area 2.00 m2 each second. Using the most general form of Newton’s second law, what is the force on the mirror?

1. 1.33 × 10^-5 N
2. 1.33 × 10⁻⁶ N
3. 1.33 × 10⁻⁷ N
4. 1.33 × 10⁻⁸ N