Tag: electromagnetic waves

Questions Related to electromagnetic waves

Fluorescent tubes give more light than a filament bulb of same power because

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. the tube contains gas at low temperature

  2. ultraviolet light is converted into visible light by fluorescence

  3. light is diffused through the walls of the tube

  4. it produces more heat than bulb

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Correct Option: B
Explanation:

The tubelight has coating of fluorescent material which converts ultra violet light into visible light. Hence the light is more intense. 

For transmission of speeches, talks, music, dramas etc ........... is used

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. radio broadcast transmitter

  2. radio telegraph transmitter

  3. navigation transmitter

  4. None of these

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Correct Option: A
Explanation:

$Answer:-$ A

Radio Broadcast Transmitters: -Theses transmitters are designed for transmitting speeches, talks, music, dramas etc for the information and reception of people. These broadcast transmitters may be either amplitude modulated or frequency modulated. The A.M transmitters operate on long waves, medium waves and short waves and radiate carrier power as low as about 1 kW and high as 100 kW. The F.M broadcast transmitters operate on very short waves or on ultra waves and radiate carrier power of the order of 100 kW or so.

Astronauts communicate with one another on moon with the help of.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. radio waves

  2. sound waves

  3. ultrasound waves

  4. infrasound waves

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Correct Option: A
Explanation:

Answer is A.

Astronauts communicate with each other in space when they are spacewalking through the use of radio waves. Radio wave signal are sent to their headsets which then translates the signal into the form of sound . When receiving and sending message to earth it is sent in the form of radio waves which is then translated to sound wave (message) by a radio set. 

In which one of the following regions of the electromagnetic spectrum will the vibrational motion of molecules give rise to absorption?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Ultraviolet

  2. Microwaves

  3. Infrared

  4. Radio waves

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Correct Option: B
Explanation:

Molecular spectra due to vibrational motion lie in the microwave region of electromagentic spectrum. Due to Kirchhoff's law in spectroscopy the same will be absorbed.

The heat in solar radiation is mainly due to the presence of _______ .

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. infrared radiations

  2. ultraviolet radiations

  3. visible light

  4. x-rays

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Correct Option: A

_________ are useful in studying the structures of crystals. 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. All electromagnetic radiations

  2. Light rays

  3. X-rays

  4. $\gamma$-rays

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Correct Option: C
Explanation:

X-rays are useful in studying the structures of crystals

Why does radio reception improve slightly during the night ? 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. The outside noise is reduced very much at night.

  2. Unlike the daytime, only a few radio stations broadcast during the night.

  3. Sunlight affects radio broadcasts to some extent during the day.

  4. The magnetic field of the earth acts with reduced intensity during the night, thereby reducing its impact on broadcasts.

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Correct Option: C
Explanation:

Answer is C.

The D region is the lowest of the regions within the ionosphere that affects radio communications signals to any degree. It is present at altitudes between about 60 and 90 kilometers and the radiation within it is only present during the day to an extent that affects radio waves noticeably. It is sustained by the radiation from the Sun and levels of ionization fall rapidly at dusk when the source of radiation is removed. It mainly has the affect of absorbing or attenuating radio communications signals particularly in the LF and MF portions of the radio spectrum, its affect reducing with frequency. At night it has little effect on most radio communications signals although there is still a sufficient level of ionization for it to refract VLF signals.
Hence, radio reception improve slightly during the night because, sunlight affects radio broadcasts to some extent during the day.

When an object absorb waves  and  energy their temperature increases.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. True

  2. False

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Correct Option: A

Infrared radiation was discovered in $1800$ by.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. William Wollaston

  2. William Herschel

  3. Wilhelm Roentgen

  4. Thomas Young

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Correct Option: B
Explanation:

Infrared radiation was discovered in $1800$ by $William Herschel$.

They discovered $\longrightarrow $ When sunlight went through various color filters; it produces different amount of heat. He hypothesized that colors could have different temperatures. He then passed light through glass prism, creating a color spectrum and analysing each color's temperature. He used three special thermometers.
For each color, one was placed within its bounds while the other two were outside as controls. The thermometer in the color had higher temperature than the others, and he found that each color going from violet to red was warmer than the last. He then placed a thermometer next to red light, where no color from spectrum were visible. He noticed that area had even higher temperature than color sections. He demonstrated that this visible type of light refracted and reflected the same way sunlight did.This light came to be known as infrared radiation.

Of the following waves has the longest wavelength?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. X-rays

  2. Green light

  3. Orange light

  4. Microwaves

  5. Gamma rays

Show answer
Correct Option: D
Explanation:

Order of wavelength from shortest to longest :      

 Gamma rays < X-rays < Green light < Orange light < Microwaves 
Thus Microwaves has the longest wavelength.