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11. As per the WHO, the safe noise level for a city is _____.
A. 45 dB
B. 50 dB
C. 55 dB
D. 60 dB
ANSWER:A
SOLUTION :According to the World Health Organization (WHO), the safe noise level for a city is 45 decibels (dB). This sound intensity is considered safe and not uncomfortable. Noise levels above 70 dB may cause ear discomfort, and continuous noise levels above 90 dB can cause hearing loss and irreversible changes in the nervous system.
12. The tolerable limit of noise for human being is around ___.
A. 25 decibel
B. 80 decibel
C. 125 decibel
D. 155 decibel
ANSWER:B
SOLUTION:The safe limit of sound for our ears is from 0 to 80 dB.
13. Sound above what level is considered hazardous noise pollutions?
A. 30 dB
B. 100 dB
C. 80 dB
D. 120 dB
ANSWER:C
SOLUTION:Sounds above 80 decibels (dB) are considered hazardous noise pollution. Decibels are the standard unit for measuring noise. For example, a normal conversation is around 60 dB, while 80 dB is when sound becomes physically painful.
14. The optimum sound level for human beings is ___.
A. 90 dB
B. 60 dB
C. 120 dB
D. 100 dB
ANSWER:B
SOLUTION:The sound level which is comfortable for the human ear is about 60 to 65 decibels
15. Which of the following has the longest wavelength?
A. Infrared
B. X-rays
C. Visible light
D. Radio waves
ANSWER:D
SOLUTION:Radio waves have the longest wavelength in the electromagnetic spectrum, ranging from the size of a football to larger than the planet. Radio waves have frequencies from 300 GHz to 3 kHz, and wavelengths from 1 millimeter to 100 kilometers.
16. Which one of the following does a TV remote control unit use to operate a TV set?
A. Light waves
B. Sound waves
C. Micro waves
D. Radio waves
ANSWER:D
SOLUTION :Most remote controls send signals using infrared radiation, though some use radio waves instead. In infrared radiation TV and remote control have to be in straight line for functioning while in Radio waves TV can even be controlled from another room.
17. Which type of electromagnetic radiation is used in the remote control of a television?
A. Infrared
B. Ultraviolet
C. Visible
D. None of these
ANSWER:A
SOLUTION:Infrared is a type of electromagnetic radiation is used in the remote control of a television. Infrared is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye.
18. The Doppler’s effect is applicable for ____.
A. Light waves
B. Sound waves
C. Space waves
D. Both a and B
ANSWER:D
SOLUTION: The Doppler effect is applicable to both sound and light waves, when the source and the observer are in motion relative to each other. The Doppler effect causes an apparent change in the frequency of the sound or light waves.
19. In television broadcast, the picture signals are transmitted by _____.
A. Amplitude modulation
B. Frequency modulation
C. Phase modulation
D. Angle modulation
ANSWER:A
SOLUTION: Amplitude Modulation (AM) is preferred for picture transmission on TV because of the following reasons: The distortion which arises due to interference between multiple signals is more in FM than AM because the frequency of the FM signal continuously changes.
20. The technique used to transmit audio signals in television broadcast is _____.
A. Amplitude modulation
B. Pulse code modulation
C. Frequency modulation
D. Time dimension multiplication
ANSWER:C
SOLUTION: In Analog TV broadcast, Audio signals are transmitted by Frequency Modulation (FM), while video signals are transmitted by Amplitude Modulation (AM).