Electromagnetic waves and modern communications

Which of the following statements about electromagnetic waves and sound waves is incorrect?

• Electromagnetic waves and sound waves can both propagate in a vacuum.

• Electromagnetic waves and sound waves cannot propagate in a vacuum.

Which of the following statements about electromagnetic waves and sound waves is incorrect?

• Electromagnetic waves and sound waves can both propagate in a vacuum

• Electromagnetic waves and sound waves can both transmit information

• Electromagnetic waves and sound waves both have energy

• Sonar systems use ultrasound for positioning

Which of the following statements about various waves encountered in life is correct?

• Electromagnetic waves can transmit information, while sound waves cannot

• Mobile phones involve both electromagnetic waves and sound waves during calls

• The propagation speed of sound waves and electromagnetic waves is the same

• The infrared rays emitted by remote controls cannot propagate in a vacuum

Among the components of electromagnetic waves, which wavelength is used by the remote control of a television?

• Gamma rays

• Visible light

• Infrared rays

• Radio waves

Which of the following devices works using the information characteristics of electromagnetic waves?

• Mobile phone

• Disinfection cabinet

• Microwave oven

• Hair dryer

Given that the wavelength in a vacuum of electromagnetic waves is λmicrowave > λinfrared > λultraviolet, what can be said about their frequencies?

• fmicrowave = finfrared = fultraviolet

• fmicrowave > finfrared > fultraviolet

• fmicrowave < finfrared < fultraviolet

• fultraviolet < fmicrowave < finfrared

In 1966, Chinese physicist Gao Kun proposed the concept of fiber optic communication. What is the carrier of information transmitted by fiber optic communication?

• Electric current

• Ultrasound

• Radio waves

• Light waves

Now vehicles often install GPS receivers to receive signals emitted by satellites for precise positioning and navigation. What is the medium through which satellites transmit information to GPS receivers?

• Laser

• Electromagnetic waves

• Infrared rays

• Ultraviolet rays

The scientific detection instruments such as laser array devices transmit images and data to Earth through (fill in 'sound wave' or 'electromagnetic wave'). If the distance from the Moon to Earth is 3.8×10^5 km, then the time to transmit information from the Moon to Earth is (c=3×10^5 km/s, keep two decimal places).

• Sound wave

• Electromagnetic wave

An aircraft that can effectively avoid radar detection is called a 'stealth aircraft'. Its surface has a special material that can (fill in 'enhance' or 'weaken') the absorption of electromagnetic waves; its surface is shaped specially, and the intensity of the electromagnetic waves emitted by the radar is (fill in 'enhance' or 'weaken') when encountering the aircraft.

• Enhance

• Weaken