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Lesson: Energy, Power, and Intensity of Electromagnetic Waves

Worksheet: Energy, Power, and Intensity of Electromagnetic Waves • 6 Questions

Q1:

What is the intensity of an electromagnetic wave with a peak electric field strength of 125 V/m?

Q2:

An outdoor WiFi unit for a picnic area has a 100-mW output and a range of about 30 m. What output power would reduce its range to 12 m for use with the same devices as before? Assume there are no obstacles in the way and that microwaves into the ground are simply absorbed.

Q3:

A 150-W lightbulb emits of its energy as electromagnetic radiation. What is the magnitude of the average Poynting vector 10.0 m from the bulb?

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

Q4:

At the top of Earth’s atmosphere, the time-averaged Poynting vector associated with sunlight has a magnitude of 1.40 kW/m2.

What is the maximum value of the electric field magnitude for a wave of this intensity?

What is the maximum value of the magnetic field magnitude for a wave of this intensity?

  • A T
  • B T
  • C T
  • D T
  • E T

What is the total power radiated by the sun? Assume that the Earth is m from the Sun and that sunlight is composed of electromagnetic plane waves.

  • A W
  • B W
  • C W
  • D W
  • E W

Q5:

The specific heat capacity of spaghetti is . 0.400 kg of spaghetti occupies a circular area 20.0 cm in diameter inside a microwave oven. On its highest power setting, the oven increases the temperature of the spaghetti by in 120 s.

What was the rate of energy absorption by the spaghetti, assuming that the spaghetti was perfectly absorbing?

Find the average intensity of the microwaves.

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

What is the peak electric field strength of the microwave?

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

What is the peak magnetic field strength of the microwave?

  • A T
  • B T
  • C T
  • D T
  • E T
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