Electromagnetic Waves Questions and Answers

Answer: B

X-rays are electromagnetic radiations.

X-rays are electromagnetic waves of very short wavelength, roughly 0.01 to 10 nm, produced when fast electrons strike a metal target. Like light, they carry no charge, travel at the speed of light and are not deflected by electric or magnetic fields.

Streams of positive ions (canal rays), electrons (cathode rays) and neutrons are particle beams; their being deflected or having mass distinguishes them from X-rays.

Answer: D

X-rays are affected by neither electric nor magnetic fields.

X-rays are electromagnetic waves, streams of photons that carry no electric charge. A charged particle is deflected by electric and magnetic fields, but an uncharged photon travels straight through them.

This is how X-rays were shown to differ from cathode rays (electrons), which are bent by both fields. So the options saying they are affected by one or both fields are wrong.

Answer: D

X-rays are electromagnetic radiation.

X-rays are electromagnetic waves of very short wavelength, roughly 0.01 to 10 nanometres, lying between ultraviolet and gamma rays. Discovered by Wilhelm Rontgen in 1895, they are produced when fast electrons strike a metal target, and they carry no charge.

Because they are uncharged, they are not deflected by electric or magnetic fields, which rules out 'positive charge' and 'negative charge'. They come from high-energy electrons, not from chemical reactions.

Answer: C

X-ray wavelengths are of the order of 1 Å (10⁻¹⁰ m).

X-rays span roughly 0.01 to 10 nm, and the X-rays used in diffraction typically have wavelengths of about 1 Å, comparable to the spacing of atoms in crystals, which is why crystals diffract them.

Wavelengths of 1 m and 1 kilometre belong to radio waves, and 1 cm to microwaves. Visible light, for comparison, lies between about 4,000 and 7,000 Å, thousands of times longer than X-rays.

Answer: C

Of the ranges offered, microwaves lie in 1 GHz - 300 GHz.

Microwaves are usually defined as electromagnetic waves from about 300 MHz to 300 GHz, wavelengths of 1 m down to 1 mm; many engineering texts start the band at 1 GHz. Either way the range from 1 GHz to 300 GHz is microwave, used for radar, satellite links, mobile phones and microwave ovens (about 2.45 GHz).

300 kHz-3 MHz is the medium-frequency band of AM radio, 3-300 MHz covers shortwave (HF) and VHF radio, and 300 GHz-400 THz is the infrared region.

Answer: B

The highest frequency belongs to X-rays.

In order of increasing frequency, the electromagnetic spectrum runs: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. X-rays have frequencies of roughly 10¹⁶ to 10¹⁹ Hz, far above infrared (about 10¹² to 10¹⁴ Hz).

Radio waves have the lowest frequency and longest wavelength of all, and microwaves come just above them, so neither competes.