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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?
Identify the part of the electromagnetic spectrum which is suitable for radar system used in aircraft navigation.
Identify the part of the electromagnetic spectrum which is:
produced by bombarding a metal target by high speed electrons.
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1019 Hz belong?
A radio can tune in to any station in the 7.5 MHz to 12 MHz band. What is the corresponding wavelength band?
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
Why are infra-red waves often called heat waves? Explain.
State Moseley's law
Arrange the following radiations in the order of their increasing wavelength:
X-rays, infrared rays, ratio waves, gamma ray and microwaves.
A wave has a wavelength of 10-3 nm. Name the wave.
What is the range of the wavelength of the following electromagnetic waves?
(A) Radio waves.
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 shorter than 4 × 10-7 m.
Name the waves produced by the changes in the nucleus of an atom.
Name the waves of wavelength nearly 0.1 nm.
Name three properties of ultraviolet radiations which are similar to visible light.
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation,
(a) the intensity increases
(b) the minimum wavelength increases
(c) the intensity remains unchanged
(d) the minimum wavelength decreases.
A certain element emits Kα X-ray of energy 3.69 keV. Use the data from the previous problem to identify the element.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
The distance between the cathode (filament) and the target in an X-ray tube is 1.5 m. If the cutoff wavelength is 30 pm, find the electric field between the cathode and the target.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Suppose a monochromatic X-ray beam of wavelength 100 pm is sent through a Young's double slit and the interference pattern is observed on a photographic plate placed 40 cm away from the slit. What should be the separation between the slits so that the successive maxima on the screen are separated by a distance of 0.1 mm?
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.
-
- Calculate the speed of the wave.
- Name the medium through which it is traveling.
State the name and the range of wavelength of the invisible electromagnetic waves beyond the red end of the visible spectrum.
Name the radiation which can be detected by thermopile.
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 two sources of infrared radiation.
State three properties of infrared radiations similar to that of visible light.
State three properties of ultra-violet radiation similar to visible light.
Choose the correct option.
The EM wave emitted by the Sun and responsible for heating the Earth’s atmosphere due to greenhouse effect is
Answer briefly.
Why are microwaves used in radar?
Answer briefly.
Give two uses of radio waves.
Name the e.m. waves which are suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves.
X-rays, gamma rays and microwaves travelling in a vacuum have ______.
Ozone layer above the earth's atmosphere will
All components of the electromagnetic spectrum in a vacuum have the same ______
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?
Write two uses of the following radiation.
Gamma rays
Electromagnetic waves of wavelengths λ1, λ2 and λ3 are used in a radar system, in water purifiers and in remote switches of TV, respectively.
- Identify the electromagnetic waves.
- Write one source for each of them.
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.
Name one radiation having the wavelength longer than the wavelength of these radiations.
In an atom X, electrons absorb the energy from an external source. This energy “excites” the electrons from a lower-energy level to a higher-energy level around the nucleus of the atom. When electrons return to the ground state, they emit photons.
The figure below is the energy level diagram of atom X with three energy levels, E1 = 0.00eV, E2 = 1.78eV and E3 = 2.95eV. The ground state is considered 0 eV for reference. The transition of electrons takes place between levels E1 and E2.
- What wavelength of radiation is needed to excite the atom to energy level E2 from E1?
- Suppose the external source has a power of 100 W. What would be the rate of photon emission?
