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Worksheet: Photons

Q1:

A photon has an energy of 20.0 keV.

What is this photon’s frequency?

  • A Hz
  • B Hz
  • C Hz
  • D Hz
  • E Hz

What is this photon’s wavelength?

  • A m
  • B m
  • C m
  • D m
  • E m

Q2:

A -ray photon has a momentum of kg⋅m/s.

Find the photon’s wavelength.

Find the photon’s energy.

Q3:

An AM radio transmitter radiates W of electromagnetic radiation at a frequency of Hz. How many photons per second does the transmitter emit?

  • A
  • B
  • C
  • D
  • E

Q4:

In the 1980s, the term picowave was used to describe food irradiation in order to overcome public resistance by playing on the well-known safety of microwave radiation. Find the energy in MeV of a photon having a wavelength of 1.00 picometers.

Q5:

What is the momentum of a 4.00-cm-wavelength photon?

  • A kg⋅m/s
  • B kg⋅m/s
  • C kg⋅m/s
  • D kg⋅m/s
  • E kg⋅m/s

Q6:

What is the energy of a photon whose momentum is kg⋅m/s?

Q7:

A photon has a 1.00-Å wavelength.

Find the photon’s momentum.

  • A kg⋅m/s
  • B kg⋅m/s
  • C kg⋅m/s
  • D kg⋅m/s
  • E kg⋅m/s

Find the photon’s energy.

Q8:

The momentum of light, as it is for particles, is exactly reversed when a photon is reflected straight back from a mirror, assuming negligible recoil of the mirror. The change in momentum is twice the photon’s incident momentum, as it is for the particles. Suppose that a beam of light has an intensity 1.00 kW/m2 and falls on a 2.00 m2 area of a mirror and reflects from it.

How much energy is reflected in 1.00 s?

How much momentum is imparted to the mirror?

  • A kg⋅m/s
  • B kg⋅m/s
  • C kg⋅m/s
  • D kg⋅m/s
  • E kg⋅m/s

How much force is exerted on the mirror?

  • A N
  • B N
  • C N
  • D N
  • E N

Q9:

Radiation known as the solar wind is incident on the top of Earth’s atmosphere has with average intensity of 1.30 kW/m2. Suppose that you are building a solar sail that will use the radiation pressure of the solar wind to propel a small toy spaceship with a mass of 0.100 kg. The sail is made from a material, which perfectly reflects radiation of the solar wind. To assess whether such a project is feasible, answer the following questions, assuming that radiation photons are incident only in normal direction to the sail reflecting surface.

What is the radiation pressure of the solar wind on the solar sail?

  • A N/m2
  • B N/m2
  • C N/m2
  • D N/m2
  • E N/m2

How much acceleration of the toy spaceship would the solar sail produce if the sail’s area is 10.0 m2?

  • A m/s2
  • B m/s2
  • C m/s2
  • D m/s2
  • E m/s2

How much velocity increase of the toy spacecraft would the sail produce in one day’s acceleration? Consider one day as seconds.