Sound waves having frequency higher than 20,000 Hz are called:
Ultrasonic
Infrasonic
Audible
Echo
How many tubes or electron guns used in a colour television set:
Two
Four
Five
Three
1 bel=
0.1 dB
10 dB
100 dB
0.01 dB
The frequency of silent whistle is:
20,000 Hz – 25000Hz
2000 Hz – 2500Hz
200 KHz – 2000 Hz
25000 KHz