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प्रश्न
Identify the electromagnetic radiation and write its wavelength range, which is used to kill germs in water purified. Name the two sources of these radiations.
उत्तर
Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, gamma rays, and cosmic rays provide the whole range (electromagnetic spectrum) in increasing frequency and decreasing wavelength order. The type of radiation and their frequency and wavelength ranges are as follows:
| Types of Radiation | Frequency Range (Hz) | Wavelength Range |
| Gamma-rays | 1020 - 1024 | < 10-12 m |
| X-rays | 1017 - 1020 | 1 nm - 1 pm |
| Ultraviolet | 1015 - 1017 | 400 nm - 1 nm |
| Visible | 4 × 1014 - 7.5 × 1014 | 750 nm - 400 nm |
| Near-infrared | 1 × 1014 - 4 × 1014 | 2.5 µm - 750 nm |
| Infrared | 1013 - 1014 | 25 µm - 2.5 µm |
| Microwaves | 3 × 1011 - 1013 | 1 mm - 25 µm |
| Radio waves | < 3 × 1011 | > 1 mm |
In water purifiers, ultraviolet light is utilised to kill bacteria. The sun is the most powerful source of UV radiation.
UV lamps, arc welding, and mercury vapour lamps are examples of man-made ultraviolet sources. Carbon, Xenon, and other arcs are some of the devices that release UV radiation.
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संबंधित प्रश्न
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).
(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
(c) 2.7 K [temperature associated with the isotropic radiation filling all space-thought to be a relic of the ‘big-bang’ origin of the universe].
(d) 5890 Å - 5896 Å [double lines of sodium]
(e) 14.4 keV [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method (Mössbauer spectroscopy)].
The small ozone layer on top of the stratosphere is crucial for human survival. Why?
Why is exposure to X-rays injurious to health but not exposure to visible light, when both are electromagnetic waves?
One of the following wavelengths is absent and the rest are present in the X-rays coming from a Coolidge tube. Which one is the absent wavelength?
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.)
Answer briefly.
Why are microwaves used in radar?
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:
Radio waves of constant amplitude can be generated with.
Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.
Name one radiation having the wavelength longer than the wavelength of these radiations.
