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प्रश्न
Give a reason for the following:
Long-distance radio broadcasts use short-wave bands. Why?
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उत्तर
Long distance radio broadcasts use shortwave bands because only these bands can be refracted by the ionosphere.
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?
What physical quantity is the same for X-rays of wavelength 10−10 m, red light of wavelength 6800 Å and radiowaves of wavelength 500 m?
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?
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If the current in the circuit for heating the filament is increased, the cutoff wavelength
Mark the correct options.
(a) An atom with a vacancy has smaller energy that a neutral atom.
(b) K X-ray is emitted when a hole makes a jump from the K shell to some other shell.
(c) The wavelength of K X-ray is smaller than the wavelength of L X-ray of the same material.
(d) The wavelength of Kα X-ray is smaller than the wavelength of Kβ X-ray of the same material.
What potential difference should be applied across an X-ray tube to get X-ray of wavelength not less than 0.10 nm? What is the maximum energy of a photon of this X-ray in joule?
(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 |
The short-wavelength limit shifts by 26 pm when the operating voltage in an X-ray tube is increased to 1.5 times the original value. What was the original value of the operating voltage?
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Name the scientist who discovered radio waves
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Identify the part of the electromagnetic spectrum used in
(i) radar and
(ii) eye surgery. Write their frequency range.
Gamma rays and radio waves travel with the same velocity in free space. Distinguish between them in terms of their origin and the main application.
How will you investigate the existence of the radiation beyond the red and violet extremes of the spectrum?
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State two uses of infrared radiations.
Choose the correct option.
Earth’s atmosphere is richest in
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For television broadcasting, the frequency employed is normally
Find the photon energy in units of ev for electromagnetic wave if waves length 40 m. Given h = 6.63 × 10–34 J.
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Write two uses of the following radiation.
X-rays
Which is the correct ascending order of wavelengths?
Which one of the following electromagnetic radiation has the least wavelength?
Below is an incomplete table showing the arrangement of electromagnetic spectrum in the increasing order of their wavelength. Complete the table:
| Gamma ray | X - ray | UV rays | Visible rays | Infrared | A | Radio waves |
- Identify the radiation A.
- Name the radiation used to detect fracture in bones.
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What is the speed of radio waves in vacuum?
Name the electromagnetic radiation that has been used in obtaining the image below.
What is called the invisible spectrum?
At what speed do all electromagnetic waves travel in a vacuum?
How do the wavelengths and frequencies of microwaves compare with those of radio waves?
Which devices commonly produce microwaves?
How does the frequency of infrared radiation compare with that of microwaves?
Which set consists of applications of infrared radiation?
Where do ultraviolet rays lie relative to visible light?
What can result from excess ultraviolet exposure?
