Which parts of the electromagnetic spectrum complete the list of applications?
Mobile phones use ……1…… .
Security scanners use ……2…… .
Intruder alarms use ……3…… .
Correct Answer: \( \boxed{\mathrm{D}} \)
Different regions of the electromagnetic spectrum have different practical applications.
Mobile phones use microwaves because microwaves can carry large amounts of information and are suitable for wireless communication.
Security scanners use X-rays because X-rays can penetrate many materials and reveal objects hidden inside luggage or packages.
Intruder alarms commonly use infrared radiation to detect the heat emitted by people moving within a monitored area.
Therefore:
\(1 =\) microwaves
\(2 =\) X-rays
\(3 =\) infrared
This combination corresponds to Option D.
Hence, the correct answer is (D).
A person exposed to excessive radiation from certain parts of the electromagnetic spectrum is likely to suffer cell damage.
Which radiations cause cell damage?
Correct Answer: \( \boxed{\mathrm{A}} \)
Electromagnetic waves with very high frequencies carry large amounts of energy. These high-energy waves can ionise atoms and molecules inside living cells, causing damage to biological tissue.
Ultraviolet (UV) radiation can damage skin cells and eye tissues and may increase the risk of skin cancer after prolonged exposure.
Gamma rays have even higher frequencies and energies. They are highly penetrating and can damage cells, tissues, and DNA deep within the body.
Visible light, such as green and red light, and radio waves are non-ionising radiations and do not normally cause this type of cell damage.
Therefore, the radiations that can cause cell damage are gamma rays and ultraviolet radiation.
Hence, the correct answer is (A).
Which type of radiation does a remote controller use to send its instructions to a television (TV)?
Correct Answer: \( \boxed{\mathrm{B}} \)
Television remote controllers communicate by sending coded pulses of electromagnetic radiation to a sensor on the TV.
The radiation used is infrared (IR), which lies just beyond the red end of the visible spectrum.
Infrared radiation is ideal for short-range communication because it is safe, inexpensive to generate, and does not easily interfere with devices in other rooms.
Gamma rays and X-rays are high-energy ionising radiations used in medical and industrial applications, while ultraviolet radiation is commonly used for sterilisation and security marking.
Therefore, remote controllers use infrared radiation to transmit instructions to a television.
Hence, the correct answer is (B).
