LED Bulb and LED Television

Q.

Which of the following electromagnetic waves is used in telecommunication?

1. radio waves

2. visible radiations

3. ultraviolet rays

4. microwaves

Q.

A device which is commonly used to convert an electrical signal into a visual signal.

1. Coolidge Tube

2. Oscilloscope

3. Electron Tube

4. Cathode ray tube

Q.

One of the uses of a cathode ray tube is

1. They are used in mobile phones and WIFI

2. They are used to break DNA molecules

3. They are used to check the waveforms of electric signals

4. They are used in dental practices

Q.

Two distinct sets of data can be used to see if there is any interference.

1. Sodium lamps

2. Fluorescent tubes

3. Lasers

4. None of these

Q. The diagram in fig. shows a source S placed in a thick lead walled container. The radiation given out is allowed to pass through a magnetic field. The magnetic field (shown as x) acts perpendicular to the plane of paper inwards. Arrows show the paths of the radiations A, B and C. Explain clearly how you used the diagram to find the radiations A, B, and C.

Q.

In a video signal for transmission of the picture, what value of bandwidth is used in communication system?

1. $2.4MHz$

2. $4.2MHz$

3. $24MHz$

4. $42MHz$

Q.

The bandwidth sufficient for commercial telephonic communication:

Q.

Which of the following frequencies will be suitable for horizontal communication using sky waves?

Q. find the wavelength of electromagnetic waves of frequency five into ten to power nine Hertz in free space wite its two applications

Q.

What is pulse code modulation in digital communication?

Q. Who invented the television ?

Q. In television transmission, the VF signals are amplified and modulated on :

1. Sound waves
2. Carrier waves
3. VF waves
4. Light waves

Q. Explain the function of a vidicon camera tube.

Q. Identify the earthing pin in the plug:

1. 
2. 
3. 
4. 

Q. The _________ are amplified and transmitted through antenna during T.V broadcasting.

1. demodulated waves
2. modulated waves
3. transmitted waves
4. None of these

Q. Depending upon the frequency of the ____________ emitted by remote control, a channel is selected, by the ________ sensor.

1. infrared radiations, microwave
2. X-rays, X-ray
3. infrared radiations, infrared
4. radio waves, infrared

Q. Label the parts of an incandescent lamp.

1. Nitrogen gas
2. Tungsten
3. Lead wire

Q. Which of the following are types of lamp?

1. Incandescent
2. Discharge
3. Fluorescent
4. Compact Fluorescent
5. LED
6. Arc Lamps
7. Wooden
8. Opaque

Q. Pair the following cards having switches with their usages.

1. Game stations
2. 
3. 
4. 
5. Door bells
6. Ceiling fans
7. High insulation
8. 

Q. Television signals broadcast from the moon can be received on the earth broadcast from Delhi cannot be received at places about $100km$ distance from Delhi. This is because

1. There is no atmosphere around the moon
2. Of strong gravity effect on TV signals
3. TV signals travel straight and cannot follow the curvature of the earth
4. There is atmosphere around the earth

Q. Which device is used for transmitting TV signals over long distances?

Q. Radioactive transmitter transmits at 830 kHz. At a certain distance from transmitter, magnetic field has amplitude 4.82x10^-11 T. Electric field and wavelength are:

Q. Normally cathode ray tube is also called as:

1. scanner
2. detector
3. transmitter
4. modulator

Q. The purpose of dividing each frame into two field so as to transmit $50$ views of the picture per second is

1. That $50Hz$ is the power line frequency in India
2. The fact that handling of higher frequencies is easier
3. To avoid flicker in the picture
4. To avoid unwanted noises in the signals