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

Microwaves are detected by

  1. barometer

  2. point contact diodes

  3. thermopiles

  4. the eye
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Point contact diodes, commonly called crystals, are the oldest microwave semiconductor devices. Unlike the pn-junction diode, the point-contact diode depends on the pressure of contact between a point and a semiconductor crystal for its operation.One section of the diode consists of a small rectangular crystal of n-type silicon. A fine beryllium-copper, bronze-phosphor, or tungsten wire presses against the crystal and forms the other part of the diode During the manufacture of the point contact diode, a relatively large current is passed from the the wire to the silicon crystal. The result of this large current is the formation of a small region of p-type material around the crystal in the vicinity of the point contact. Thus, a pn-junction is formed which behaves in the same way as a normal pn-junction. The pointed wire is used instead of a flat metal plate to produce a high-intensity electric field at the point contact without using a large external source voltage.

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

State whether given statement is True or False

MRI uses radio-waves.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create detailed images of the organs and tissues within your body.

Most MRI machines are large, tube-shaped magnets. When you lie inside an MRI machine, the magnetic field temporarily realigns hydrogen atoms in your body. Radio waves cause these aligned atoms to produce very faint signals, which are used to create cross-sectional MRI images like slices in a loaf of bread.

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

Radio waves do not penetrate in the band of

  1. ionosphere

  2. mesosphere

  3. troposphere

  4. stratosphere
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Answer:-$ A option

The ionization of gas particles in the ionosphere aids in the transmission of radio waves by reflecting waves back to Earth, rather than allowing them to escape the atmosphere. Solar flares, the spontaneous eruption of high-energy radiation from the surface of the sun, can cause a sharp increase in the number of ionized particles in the upper atmosphere and can interfere with radio wave transmissions.

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

A radar sends the waves towards a distant object and receives the signal reflected by object. These waves are

  1. sound waves

  2. light waves

  3. radio waves

  4. microwaves
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

$Answer:-$ C and D option

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwave domain, an emitting antenna, a receiving antenna (separate or the same as the previous one) to capture any returns from objects in the path of the emitted signal, a receiver and processor to determine properties of the object(s).

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

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

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

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

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

  1. radio broadcast transmitter

  2. radio telegraph transmitter

  3. navigation transmitter

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. radio waves

  2. sound waves

  3. ultrasound waves

  4. infrasound waves
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

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

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

  1. Ultraviolet

  2. Microwaves

  3. Infrared

  4. Radio waves
Reveal answer Fill a bubble to check yourself
B Correct answer
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.