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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?

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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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अध्याय 13: Electromagnetic Waves and Communication System - Exercises [पृष्ठ २४१]

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

वीडियो ट्यूटोरियलVIEW ALL [2]

संबंधित प्रश्न

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


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?


If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?


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


State Moseley's law


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

(a) Visible. 


Name two electromagnetic waves of frequency smaller than that of violet light. State one use of each.


Name three properties of ultraviolet radiations which are similar to visible light.


Which part of electromagnetic spectrum is used in radar systems?


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


Frequencies of Kα X-rays of different materials are measured. Which one of the graphs in the figure may represent the relation between the frequency v and the atomic number ?


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


X-ray incident on a material
(a) exerts a force on it
(b) transfers energy to it
(c) transfers momentum to it
(d) transfers impulse to it.


Iron emits Kα X-ray of energy 6.4 keV. Calculate the times taken by an iron Kα photon to cross through a distance of 3 km.

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


The Kβ X-ray of argon has a wavelength of 0.36 nm. The minimum energy needed to ionize an argon atom is 16 eV. Find the energy needed to knock out an electron from the K shell of an argon atom.


The Kβ X-rays from certain elements are given below. Draw a Moseley-type plot of √v versus Z for Kβ radiation.

Element Ne P Ca Mn Zn Br
Energy (keV) 0.858 2.14 4.02 6.51 9.57 13.3

The Kα X-rays of aluminium (Z = 13) and zinc (Z = 30) have wavelengths 887 pm and 146 pm respectively. Use Moseley's  law √v = a(− b) to find the wavelengths of the Kα X-ray of iron (Z = 26).

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


The energy of a silver atom with a vacancy in K shell is 25.31 keV, in L shell is 3.56 keV and in M shell is 0.530 keV higher than the energy of the atom with no vacancy. Find the frequency of Kα, Kβ and Lα X-rays of silver.

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


When 40 kV is applied across an X-ray tube, X-ray is obtained with a maximum frequency of 9.7 × 1018 Hz. Calculate the value of Planck constant from these data.

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


An X-ray tube operates at 40 kV. Suppose the electron converts 70% of its energy into a photon at each collision. Find the lowest there wavelengths emitted from the tube. Neglect the energy imparted to the atom with which the electron collides.

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


The stopping potential in a photoelectric experiment is linearly related to the inverse of the wavelength (1/λ) of the light falling on the cathode. The potential difference applied across an X-ray tube is linearly related to the inverse of the cutoff wavelength (1/λ) of the X-ray emitted. Show that the slopes of the lines in the two cases are equal and find its value.

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


Name the scientist who discovered Ultraviolet rays


What are ultraviolet radiations? How are they detected? State two properties and one use of ultraviolet radiations.

An electromagnetic wave has a frequency of 500 MHz and a wavelength of 60 cm.
    1. Calculate the speed of the wave.
    2. Name the medium through which it is traveling.

To which regions of the electromagnetic spectrum do the following wavelengths belong: 
(a) 250 nm 
(b) 1500 nm 


Arrange the following electromagnetic waves in increasing order of their frequencies (i.e. begin with the lowest frequency):
Visible light, y rays, X rays, microwaves, radio waves, infrared radiations, and ultraviolet radiation.


Name the part of the electromagnetic spectrum which is: 
Suitable for radar systems used in aircraft navigation.


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


Give one use of electromagnetic radiations in Infrared radiation.


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


State two uses of infrared radiations.


Answer briefly.

Does an ordinary electric lamp emit EM waves?


Answer briefly.

What are radio waves?


Solve the numerical problem.

The speed of light is 3 × 108 m/s. Calculate the frequency of red light of a wavelength of 6.5 × 10−7 m.


An electron beam is accelerated by a potential difference V to hit a metallic target to produce X-rays. It produces continuous as well as characteristic X-rays. If λmin is the smallest possible wavelength of X-ray in the spectrum, the variation of log λmin with log V is correctly represented in:


For television broadcasting, the frequency employed is normally


If λv, λx and λm Am represents the wavelength of visible light, x-ray and microwaves respectively, then ______.


Why does microwave oven heats up a food item containing water molecules most efficiently?


The magnetic field of a beam emerging from a filter facing a floodlight is given by B0 = 12 × 10–8 sin (1.20 × 107z – 3.60 × 1015t) T. What is the average intensity of the beam?


Electromagnetic waves with wavelength

  1. λ1 is used in satellite communication.
  2. λ2 is used to kill germs in water purifies.
  3. λ3 is used to detect leakage of oil in underground pipelines.
  4. λ4 is used to improve visibility in runways during fog and mist conditions.
  1. Identify and name the part of electromagnetic spectrum to which these radiations belong.
  2. Arrange these wavelengths in ascending order of their magnitude.
  3. Write one more application of each.

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?


Given below in the left column are different modes of communication using the kinds of waves given in the right column. 

A.  Optical Fibre
Communication
P. Ultrasound
B. Radar Q. Infrared Light
C. Sonar R. Microwaves
D. Mobile Phones  S. Radio Waves

From the options given below, find the most appropriate match between entries in the left and the right column.


Photons of an electromagnetic radiation has an energy 11 keV each. To which region of electromagnetic spectrum does it belong? 


Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.


Identify the part of the electromagnetic spectrum which:

  1. produces the heating effect.
  2. is absorbed by the ozone layer in the atmosphere.
  3. is used for studying crystal structure.

Write any one method of the production of each of the above radiations.


Assertion (A): Ultraviolet radiations is scattered more as compared to the microwave radiations.

Reason (R): Wavelength of ultraviolet radiation is more than the wavelength of microwave radiation.


What happens when an electron collides with a positron?


Name the electromagnetic radiation that has been used in obtaining the image below.


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