Microwaves

Q.

A radar is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.02 milliseconds.

If the velocity of the wave is 3 x 10⁸ m s^-1, the distance of the plane from the radar station is:

1. 3000 km

2. 3 km

3. 2 km

4. 1500 km

Q.

Who discovered the ultra short radio waves?

Q.

Frequencies in the UHF(Ultra High Frequency) range normally propagate by means of:

Q.

Explain the term betatron.

Q. Why does the frequency of light remains unchanged but the wavelength of light changes while passing from one medium to other?

Q. Why food placed in a microwave oven cooks more quickly than in a normal oven?

Q. The waves used in telecommunication are.

1. Ultraviolet
2. Infra red
3. Micro waves
4. Cosmic rays

Q.

Microwaves are being used in which of the following cases?

1. For the sense of sight

2. Satellite communication/radar communication

3. Cooking/heating in the microwave oven

4. Analysis of the molecular and atomic structure

Q.

What is the principle behind the off and on of a tablet on using the flip cover?

Q. The atomic number $\left(Z\right)$ of an element whose $k_a$ wavelength is $\lambda$ is $11$. The atomic number of an element whose $k_a$, wavelength is $4\lambda$ is equal to

1. $4$
2. $44$
3. $11$
4. $6$

Q. The electromagnetic waves of frequency range $100$ to $300$GHz are used in

Q. For wireless communication of voice signal through the atmosphere, we use electromagnetic waves in the_________Region of spectrum

1. Visible
   
2. Microwave
   
3. Radiowave
   
4. Ultraviolet
   

Q. The waves relevant to telecommunications are

1. visible light
2. infrared
3. ultraviolet
4. microwave

Q. Which radiation is used for satellite communication?

1. Micro waves
2. X rays
3. Gamma rays
4. Infra red rays

Q. Assertion :- Microwave communication is preferred over optical communication.
Reason :- Microwaves provide large number of channels and band width compared to optical signals.

1. Assertion is true but reason is false.

2. Both assertion and reason are true and the reason is correct explanation of assertion.

3. Both assertion and reason are true and the reason is not the correct explanation of assertion.

4. Both assertion and reason are false.

Q. Name an electromagnetic wave which is used in the radar system used in aircraft navigation. Give another use of the wave.

Q. Name the part of the electromagnetic spectrum of wavelength ${10}^{-2}m$ and mention its one application.

Q. The frequency $2MHz$ belongs to:

1. visible light
2. X-rays
3. microwaves
4. radiowaves

Q. In which one of the following regions of the electromagnetic specturm will the vibration motion of molecules give rise to absorption?

1. Ultraviolet
2. Microwave
3. Infrared
4. Radio wave

Q. IF $v_s,v_x$ and $v_m$ are the speeds of gamma rays X-rays and microwaves respectively in vacuum, then:

1. $v_s>v_x>v_m$
2. $v_s<v_x<v_m$
3. $v_s<v_x>v_m$
4. $v_s=v_x=v_m$

Q. The part of the electromagnetic spectrum which is suitable for radar systems used in aircraft navigation :

1. X-Rays
2. Ultraviolet
3. Gamma Rays
4. Microwaves or short radiowaves

Q. The working of a microwave oven involves

1. Absorption of microwaves by matter
2. Reception of microwaves by optical fibre
3. Microwave amplification by stimulated emission of radiation
4. Transmission of microwaves through a metal

Q. Name the part of electromagnetic spectrum of wavelength ${10}^{2}m$ and mention its one application.

Q. Give one use of microwaves.

Q. How are Microwaves produced?

Q. 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

Q. The waves used by artificial satellites for communication is the

1. microwaves
2. infrared waves
3. radio waves
4. X-rays

Q.

Microwaves are being used in which of the following cases?

1. Satellite communication/radar communication

2. Cooking/heating in the microwave oven

3. Analysis of the molecular and atomic structure

4. For the sense of sight

Q. To which part of the electromagnetic spectrum does a wave of frequency $5\times {10}^{11}Hz$ belong?

Q. Maxwell’s Equations and Hertz’s Discoveries(17)
Review. A microwave oven is powered by a magnetron, an electronic device that generates electromagnetic waves of frequency $2.45GHz$. The microwaves enter the oven and are reflected by the walls. The standing-wave pattern produced in the oven can cook food unevenly, with hot spots in the food at antinodes and cool spots at nodes, so a turntable is often used to rotate the food and distribute the energy. If a microwave oven intended for use with a turntable is instead used with a cooking dish in a fixed position, the antinodes can appear as burn marks on foods such as carrot strips or cheese. The separation distance between the burns is measured to be $6cm\pm 5\%$. From these data, calculate the speed of the microwaves.