Modern Physics - Photon Momentum and de Broglie Wavelength

The electron volt is a measure of

• charge

• velocity

• electric potential

• momentum

• energy

An electron and a positron, each of mass 9.1 x 10^-31 kilogram, are in the same general vicinity and have very small initial speeds. They then annihilate each other, producing two photons. What is the approximate energy of each emerging photon?

• 0.51 Mev

• 2.0 Mev

• 4.0 Mev

• 6.6 Mev

• It cannot be determined unless the frequency of the photon is known

If photons of light of frequency f have momentum p, photons of light of frequency 2f will have a momentum of

• 1/2 p

• $\frac{1}{\sqrt{2}}$ p

• p

• $\sqrt{2}$ p

• 2p

Which of the following is true about the momentum of photons?

• Photons have no rest mass, so they have no momentum.

• The momentum of a photon is directly proportional to its energy.

• The momentum of a photon is inversely proportional to the square root of its frequency.

• Photons all travel at the speed of light, so they all have the same momentum.

• The momentum of a photon is directly proportional to its wavelength.

An electron and a positron, each of mass 9.1 x 10^-31 kilogram, are in the same general vicinity and have very small initial speeds. They then annihilate each other, producing two photons. What is the angle between the paths of the emerging photons?

• 0°

• 30°

• 45°

• 90°

• 180°

If the momentum of an electron doubles, its de Broglie wavelength is multiplied by a factor of

• 1/4

• 1/2

• 1

• 2

• 4

A photon scatters from an electron that is initially at rest, as shown above. Which of the following is true of the wavelength and frequency of the scattered photon compared to those of the incident photon?

• The wavelength increases

• The wavelength decreases

• The frequency increases

• The wavelength and frequency will remain unchanged.

Electrons that have been accelerated from rest through a potential difference of 150 volts have a de Broglie wavelength of approximately 1 x 10^-l0 meters. In order to obtain electrons whose de Broglie wavelength is 5 x 10^-ll meters, what accelerating potential is required?

• 37.5 V

• 75 V

• 300 V

• 600 V

• 22,500 V