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Give a reason for the following: It is necessary to use satellites for long-distance TV transmission. Why? - Physics

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प्रश्न

Give a reason for the following:

It is necessary to use satellites for long-distance TV transmission. Why?

टीपा लिहा
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उत्तर

  1. It is necessary to use satellites for long-distance TV transmissions because television signals are of high frequencies and high energies. Thus, these signals are not reflected by the ionosphere.
  2. Hence, satellites are helpful in reflecting TV signals. Also, they help in long-distance TV transmissions.
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पाठ 13: Electromagnetic Waves and Communication System - Exercises [पृष्ठ २४१]

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बालभारती Physics [English] Standard 11 Maharashtra State Board
पाठ 13 Electromagnetic Waves and Communication System
Exercises | Q 2. (xi) (ii) | पृष्ठ २४१

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संबंधित प्रश्‍न

To which part of electromagnetic spectrum does a wave of frequency 3 × 1013 Hz belong?


To which part of the electromagnetic spectrum does a wave of frequency 5 × 1019 Hz belong?


A radio can tune in to any station in the 7.5 MHz to 12 MHz band. What is the corresponding wavelength band?


The terminology of different parts of the electromagnetic spectrum is given in the text. Use the formula E = hv (for energy of a quantum of radiation: photon) and obtain the photon energy in units of eV for different parts of the electromagnetic spectrum. In what way are the different scales of photon energies that you obtain related to the sources of electromagnetic radiation?


Use the formula λm T= 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?


Give a reason for the following:

Long-distance radio broadcasts use short-wave bands. Why?


Why are infra-red waves often called heat waves? Explain.


(a) Give a list of at least five radiations, in order of their increasing frequencies, which make up the complete electromagnetic spectrum.

(b) Which of the radiation mentioned by you in part (a) has the highest penetrating power.


What is the range of the wavelength of the following electromagnetic waves?

(a)X-rays,


What is the range of the wavelength of the following electromagnetic waves?

(a) Infrared.


Name the rays or waves  of highest frequency .


An electromagnetic wave has a frequency of 500 MHz and a wavelength of 60 cm.name the medium through which it is travelling


The wavelength of X-rays is 0.01 Å. Calculate its frequency. State the assumption made, if any.


How are X-rays produced?


In a Coolidge tube, electrons strike the target and stop inside it. Does the target get more and more negatively charged as time passes?


Can X-rays be used for photoelectric effect?


X-ray and visible light travel at the same speed in vacuum. Do they travel at the same speed in glass?


Characteristic X-rays may be used to identify the element from which they are being emitted. Can continuous X-rays be used for this purpose?


Why is exposure to X-rays injurious to health but not exposure to visible light, when both are electromagnetic waves?


An X-ray beam can be deflected


The energy of a photon of a characteristic X-ray from a Coolidge tube comes from


The X-ray beam emerging from an X-ray tube


50% of the X-rays coming from a Coolidge tube are able to pass through a 0.1 mm thick aluminium foil. If the potential difference between the target and the filament is increased, the fraction of the X-rays passing through the same foil will be


Cutoff wavelength of X-rays coming from a Coolidge tube depends on the
(a) target material
(b) accelerating voltage
(c) separation between the target and the filament
(d) temperature of the filament.


A free atom of iron emits Kα X-rays of energy 6.4 keV. Calculate the recoil kinetic energy of the atom. Mass of an iron atom = 9.3 × 10−26 kg.

(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)


Give two properties of ultraviolet radiations which differ from the visible light.

Name three radiations and their wavelength range which are invisible and beyond the violet end of the visible spectrum.


Name the radiation which can be detected by thermopile.


Identify the part of the electromagnetic spectrum used in
(i) radar and
(ii) eye surgery. Write their frequency range.


State two properties of infrared radiations which differ from visible light.


Give one use of electromagnetic radiation in Microwaves.


Give one use of electromagnetic radiation in Ultraviolet radiation.


Name the radiations used for the detection of fracture in bones.


What is the wavelength of the wave whose frequency is 1012 Hz? Name the electromagnetic wave.


Choose the correct option.

The EM wave emitted by the Sun and responsible for heating the Earth’s atmosphere due to greenhouse effect is


Choose the correct option.

How does the frequency of a beam of ultraviolet light change when it travels from air into glass?


Answer briefly.

Why are microwaves used in radar?


Answer briefly.

Give two uses of radio waves.


Solve the numerical problem.

Calculate the frequency in MHz of a radio wave of wavelength 250 m. Remember that the speed of all EM waves in a vacuum is 3.0 × 108 m/s.


A bat moving at 10 ms−1 towards a wall sends a sound signal of 8000 Hz towards it. On reflection, it hears a sound of frequency f The value of f in Hz is close to (speed of sound = 320 ms−1)


Light of wavelength `3500A` is incident on two metals A and B whose work functions are 3.2 eV and 1.9 eV respectively. Which metal will emit photoelectrons?


All components of the electromagnetic spectrum in a vacuum have the same ______


The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is ______.


What happens to the intensity of light from a bulb if the distance from the bulb is doubled? As a laser beam travels across the length of a room, its intensity essentially remains constant. What geometrical characteristic of LASER beam is responsible for the constant intensity which is missing in the case of light from the bulb?


Arrange the following electromagnetic radiation in the ascending order of their frequencies:

X-rays, microwaves, gamma rays, radio waves


What happens when an electron collides with a positron?


What is the wavelength range of electromagnetic radiation used in radio broadcast?


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