EM waves

Which one of the following statements concerning electromagnetic waves is false?

• Electromagnetic waves are longitudinal waves.

• Electromagnetic waves transfer energy through space.

• The existence of electromagnetic waves was predicted by Maxwell.

• Electromagnetic waves can propagate through a material substance.

• Electromagnetic waves do not require a physical medium for propagation.

Note the different types of electromagnetic radiation: (1) X-rays (4) visible light

(2) radio waves (5) infrared radiation

(3) gamma rays (6) ultraviolet radiation

Which list correctly ranks the electromagnetic waves in order of increasing frequency?

• 2, 3, 4, 5, 6, 1

• 2, 5, 4, 1, 6, 3

• 2, 5, 4, 6, 1, 3

• 3, 1, 6, 4, 5, 2

• 3, 6, 1, 4, 5, 2

Which one of the following will not generate electromagnetic waves or pulses?

• a steady direct current

• an accelerating electron

• a proton in simple harmonic motion

• an alternating current

• charged particles traveling in a circular path in a mass spectrometer

Complete the following sentence: When electrons from a heated filament accelerate through vacuum toward a positive plate,

• only an electric field will be produced.

• only a magnetic field will be produced.

• electromagnetic waves will be produced.

• longitudinal waves will be produced.

• neither electric nor magnetic fields will be produced.

Which one of the following wavelengths is in the infrared range of the electromagnetic spectrum?

• 100 mm

• 100 nm

• 400 m

• 2 ´ 10^–15 m

• 20 µm

Which one of the following statements concerning electromagnetic waves is false?

• Electromagnetic waves carry energy.

• X-rays have longer wavelengths than radio waves.

• In vacuum, all electromagnetic waves travel at the same speed.

• Lower frequency electromagnetic waves can be produced by oscillating circuits.

• They consist of mutually perpendicular electric and magnetic fields that oscillate perpendicular to the direction of propagation.

Which one of the following statements concerning the wavelength of an electromagnetic wave in a vacuum is true?

• The wavelength is independent of the speed of the wave for a fixed frequency.

• The wavelength is inversely proportional to the speed of the wave.

• The wavelength is the same for all types of electromagnetic waves.

• The wavelength is directly proportional to the frequency of the wave.

• The wavelength is inversely proportional to the frequency of the wave.

When a radio telescope observes a region of space between two stars, it detects electromagnetic radiation that has a wavelength of 0.21 m. This radiation was emitted by hydrogen atoms in the gas and dust located in that region. What is the frequency of this radiation?

• 7.1 ´ 10¹⁰ Hz

• 2.1 ´ 10¹⁴ Hz

• 3.0 ´ 10⁸ Hz

• 6.9 ´ 10¹¹ Hz

• 1.4 ´ 10⁹ Hz

Complete the following sentence: The various colors of visible light differ in

• frequency only.

• wavelength only.

• their speeds in a vacuum.

• frequency and wavelength.

• frequency and their speed in a vacuum.

An FM radio station generates radio waves that have a frequency of 95.5 MHz. The frequency of the waves from a competing station have a frequency of 102.7 MHz. What is the difference in wavelength between the waves emitted from the two stations?

• 0.22 m

• 0.45 m

• 0.84 m

• 2.4 m

• 42 m