The sound level of rustling of leave is:
1 dB
20 dB
30 dB
10 dB
Sound waves having frequency higher than 20,000 Hz are called:
Ultrasonic
Infrasonic
Audible
Echo
NOT gate is also called:
Converter
Inverter
Transmitter
Receiver
How many tubes or electron guns used in a colour television set:
Two
Four
Five
Three
