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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
- 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.
- Hence, satellites are helpful in reflecting TV signals. Also, they help in long-distance TV transmissions.
संबंधित प्रश्न
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1011 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?
Give a reason for the following:
Long-distance radio broadcasts use short-wave bands. Why?
If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?
Name the high energetic invisible electromagnetic waves which help in the study of the structure of crystals
State an additional use of the X-rays waves
Why are infra-red waves often called heat waves? Explain.
What is the range of the wavelength of the following electromagnetic waves?
(a) Gamma rays.
Name the region beyond the red end of the spectrum.
What do you understand by the invisible spectrum?
State the approximate range of wavelength associated with infrared rays.
Name the radiations of wavelength just longer than 8 × 10-7m.
Name the rays or waves of highest frequency .
Name the waves produced by the changes in the nucleus of an atom.
Which part of electromagnetic spectrum is used in radar systems?
In a Coolidge tube, electrons strike the target and stop inside it. Does the target get more and more negatively charged as time passes?
Is it possible that in a Coolidge tube characteristic Lα X-rays are emitted but not Kα X-rays?
Why is exposure to X-rays injurious to health but not exposure to visible light, when both are electromagnetic waves?
Consider a photon of a continuous X-ray coming from a Coolidge tube. Its energy comes from
50% of the X-ray coming from a Coolidge tube is able to pass through a 0.1 mm thick aluminium foil. The potential difference between the target and the filament is increased. The thickness of the aluminium foil that will allow 50% of the X-ray to pass through will be
For a given material, the energy and wavelength of characteristic X-rays satisfy
(a) E(Kα) > E(Kβ) > E(Kγ)
(b) E(Mα) > E(Lα) > E(Kα)
(c) λ(Kα) > λ(Kβ) > λ(Kγ)
(d) λ(Mα) > λ(Lα) > λ(Kα).
The X-ray coming from a Coolidge tube has a cutoff wavelength of 80 pm. Find the kinetic energy of the electrons hitting the target.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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 |
Heat at the rate of 200 W is produced in an X-ray tube operating at 20 kV. Find the current in the circuit. Assume that only a small fraction of the kinetic energy of electrons is converted into X-rays.
Write the range of the wavelength of the following electromagnetic radiations:
(a) Infrared rays
(b) Ultraviolet rays
(c) γ -rays
Write one use of each of the above.
Name the scientist who discovered radio waves
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:
Produced by bombarding a metal target with high electrons.
Identify the part of the electromagnetic spectrum used in (i) radar and (ii) eye surgery. Write their frequency range.
State three properties of infrared radiations similar to that of visible light.
Give one use of electromagnetic radiation in Ultraviolet radiation.
Give one use of electromagnetic radiations in Infrared radiation.
Solve the numerical problem.
Calculate the wavelength in nm of an X-ray wave of frequency 2.0 × 1018 Hz.
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?
For television broadcasting, the frequency employed is normally
The frequency of e. m waves which is best suited .to observed of radius 3 × 10–4 his of the order of
One requires 11eV of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dissociation lies in ______.
Write two uses of the following radiation.
X-rays
The half-value thickness of an absorber is defined as the thickness that will reduce exponentially the intensity of a beam of particles by a factor of 2. The half-value thickness in (µm) for lead assuming X-ray beam of wavelength 20 pm, µ = 50 cm-1 for X-rays in lead at wavelength λ = 20 pm, is ______ µm.
Name two electromagnetic waves of wavelength smaller than that of violet light.
Which part of the electromagnetic spectrum is known as the visible spectrum?
At what speed do all electromagnetic waves travel in a vacuum?
Which description identifies how radio waves are mainly produced?
How does the frequency of infrared radiation compare with that of microwaves?
Which set consists of applications of infrared radiation?
Which part of the electromagnetic spectrum can the human eye detect?
