21. The electrical circuits used to get smooth do output from a rectified circuit is called

1. 1. Oscillator

   
   
   

   2. Full wave rectifier

   
   
   

   3. Amplifier

   
   
   

   4. Filter

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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22. Who was the inventor of Radar ?

1. 1. Robert Watson

   
   
   

   2. Fleming

   
   
   

   3. Bush Wall

   
   
   

   4. Austin

   
   
   

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1. View Hint View Answer Discuss in Forum

   Robert Watson was the inventor of Radar.

   Correct Option: A

   Robert Watson was the inventor of Radar.

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23. CT scan is done by using

1. 1. Infra-red rays

   
   
   

   2. Ultrasonic waves

   
   
   

   3. Visible lights

   
   
   

   4. X- rays

   
   
   

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1. View Hint View Answer Discuss in Forum

   CT scan is done by using X - rays.

   Correct Option: D

   CT scan is done by using X - rays.

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24. Recently developed technique for monitoring fetal growth is

1. 1. Microwave technique

   
   
   

   2. Ultrasonic

   
   
   

   3. Ultra-violet rays

   
   
   

   4. X-rays

   
   
   

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1. View Hint View Answer Discuss in Forum

   Ultrasonic is recently developed technique for monitoring foetal growth.

   Correct Option: B

   Ultrasonic is recently developed technique for monitoring foetal growth.

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25. Light from the sun reaches earth in about

1. 1. 2 minutes

   
   
   

   2. 4 minutes

   
   
   

   3. 8 minutes

   
   
   

   4. 16 minutes

   
   
   

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1. View Hint View Answer Discuss in Forum

   In about 8 minutes light from the sun reaches the earth.
   Time = Distance / Speed
   Speed of light in air / vacuum = 3 x 10⁸ ms^-1
   Distance of the earth from the sun = 1.44 x 10¹¹ m

   Correct Option: C

   In about 8 minutes light from the sun reaches the earth.
   Time = Distance / Speed
   Speed of light in air / vacuum = 3 x 10⁸ ms^-1
   Distance of the earth from the sun = 1.44 x 10¹¹ m

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