Practice portal › Electromagnetic Waves › Uses of the Bands, and lambda nu = c

Two opposite charged particles oscillate about their mean equilibrium position in free space, with a frequency of 10⁹ Hz. The wavelength of the corresponding electromagnetic wave produced is ______ cm.

Asked in GSEB Board March 2020 (old course) · Wavelength, frequency and photon energy

• (1) 30
• (2) 0.3
• (3) 3×10¹⁵
• (4) 3.0

Step-by-step solution

Why the other options are wrong

• (2) 0.3 is the wavelength in metres, and the blank is in centimetres: 0.3 m=30 cm.
• (3) comes from no single slip produces 3×10¹⁵. Sanity check: λ=c/u=0.3 m; multiplying by the frequency instead of dividing would give 3×10¹⁷ m, which is not this either.
• (4) 3.0 cm is the wave of a 10¹⁰ Hz oscillation. At 10⁹ Hz the wave is ten times longer.

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