Electromagnetic Waves: NEET MCQ practice

Answer: D. All of the above

Low frequency (LF) radio waves (30–300 kHz) can propagate through air as ground waves (used in AM radio), penetrate seawater (used for submarine communication), and are also carried by copper cables (e.g., in wired telecommunication). All three media are indeed used for LF transmission, making option (d) correct. A student might think copper cable is only for higher frequencies, but cables work for all frequencies, including LF.

Answer: B. William Herschel

Infrared radiation was discovered by William Herschel in 1800 while measuring the heating effect of different colors of sunlight. Wilhelm Roentgen discovered X-rays much later, and Thomas Young is known for the double-slit experiment. This is direct recall from physics history.

Answer: A. Infrared

Infrared radiation is used in heat therapy to relieve muscle aches because it penetrates the skin and produces a warming effect, improving blood flow and reducing pain. Ultraviolet is not used for muscle aches — it's mainly for sterilization and skin conditions. Microwaves and X-rays have entirely different medical applications and are not employed for muscle pain relief.

Answer: B. 400-700 nm

The visible fraction of light for the human eye lies in the wavelength range 400 nm to 700 nm, which is a standard fact from the electromagnetic spectrum. Options (a), (c), and (d) are incorrect because they either include non-visible ultraviolet/infrared wavelengths or miss significant parts of the visible range.

Answer: B. Maxwell

Maxwell developed the electromagnetic theory of light, predicting that light is an electromagnetic wave. Newton proposed a particle theory, Huygens proposed a wave theory (but not electromagnetic), and Planck explained quantum effects, so the other options are distractors from different chapters.