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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
Why are microwaves considered suitable for radar systems used in aircraft navigation?
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1019 Hz belong?
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1011 Hz belong?
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?
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.
The wavelengths for the light of red and blue colours are roughly 7.8 × `10^7` m and 4.8 × `10^7` m respectively.
(a) Which colour has the greater speed in vacuum?
(b) Which colour has the greater speed in glass?
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) Visible.
What is the range of the wavelength of the following electromagnetic waves?
(a) Infrared.
What do you understand by the invisible spectrum?
State the approximate range of wavelength associated with infrared rays.
Name two electromagnetic waves of frequency smaller than that of violet light. State one use of each.
Name the rays or waves of highest frequency .
Name the waves produced by the changes in the nucleus of an atom.
The wavelength of X-rays is 0.01 Å. Calculate its frequency. State the assumption made, if any.
Name of physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.
If the potential difference applied to the tube is doubled and the separation between the filament and the target is also doubled, the cutoff wavelength
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
For harder X-rays,
(a) the wavelength is higher
(b) the intensity is higher
(c) the frequency is higher
(d) the photon energy is higher.
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.
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).
Find the cutoff wavelength for the continuous X-rays coming from an X-ray tube operating at 30 kV.
(Use Planck constant h = 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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 |
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- Calculate the speed of the wave.
- Name the medium through which it is traveling.
Identify the part of the electromagnetic spectrum used in
(i) radar and
(ii) eye surgery. Write their frequency range.
Name the radiation of the electromagnetic spectrum which is used for the following:
For taking photographs of the sky during the night and foggy conditions . Give the frequency range
How will you investigate the existence of the radiation beyond the red and violet extremes of the spectrum?
A car is moving towards a high cliff. The car driver sounds a horn of frequency f. The reflected sound heard by the driver has a frequency 2f. If v be the velocity of sound, then the velocity of the car, in the same velocity units, will be:
Ozone layer above the earth's atmosphere will
Find the photon energy in units of ev for electromagnetic wave if waves length 40 m. Given h = 6.63 × 10–34 J.
What is time period of the light for which the eye is most sensitive?
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 ______.
Write two uses of the following radiation.
Gamma rays
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 electromagnetic wave whose wavelength range is from about 10-3 m to about 10-1 m. Write one use of this.
What do electromagnetic waves require for propagation?
What happens to wavelength as the frequency of electromagnetic radiation increases?
Which relation connects the speed of light in vacuum, frequency, and wavelength?
How do the wavelengths and frequencies of microwaves compare with those of radio waves?
Which devices commonly produce microwaves?
Which set lists uses of microwaves?
Which set consists of applications of infrared radiation?
Which set lists uses of ultraviolet rays?
