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प्रश्न
Answer briefly.
Why high-frequency carrier waves are used for the transmission of audio signals?
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उत्तर
An audio signal has a low frequency (< 20 kHz) and low-frequency signals cannot be transmitted over large distances. Because of this, high-frequency carrier waves are used for transmission.
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संबंधित प्रश्न
Name the parts of the electromagnetic spectrum which is
used as a diagnostic tool in medicine.
Write in brief, how these waves can be produced.
If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.
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?
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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State an additional use of the X-rays waves
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What do you understand by the statement, "Electromagnetic waves transport momentum"?
Which radiation is used for satellite communication?
Name of physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.
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
X-ray incident on a material
(a) exerts a force on it
(b) transfers energy to it
(c) transfers momentum to it
(d) transfers impulse to it.
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.
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(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
The stopping potential in a photoelectric experiment is linearly related to the inverse of the wavelength (1/λ) of the light falling on the cathode. The potential difference applied across an X-ray tube is linearly related to the inverse of the cutoff wavelength (1/λ) of the X-ray emitted. Show that the slopes of the lines in the two cases are equal and find its value.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Name three radiations and their wavelength range which are invisible and beyond the violet end of the visible spectrum.
Identify the part of the electromagnetic spectrum used in
(i) radar and
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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
Answer briefly.
Why are microwaves used in radar?
SONAR emits which of the following waves?
Electromagnetic waves with wavelength
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- λ2 is used to kill germs in water purifies.
- λ3 is used to detect leakage of oil in underground pipelines.
- λ4 is used to improve visibility in runways during fog and mist conditions.
- Identify and name the part of electromagnetic spectrum to which these radiations belong.
- Arrange these wavelengths in ascending order of their magnitude.
- Write one more application of each.
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Which one of the following electromagnetic radiation has the least wavelength?
Identify the part of the electromagnetic spectrum which:
- produces the heating effect.
- is absorbed by the ozone layer in the atmosphere.
- is used for studying crystal structure.
Write any one method of the production of each of the above radiations.
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 |
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- Name the radiation used to detect fracture in bones.
- Name one property common to both A and Radio waves.
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?
