Advertisements
Advertisements
प्रश्न
Answer briefly.
Why high-frequency carrier waves are used for the transmission of audio signals?
Advertisements
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.
APPEARS IN
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)].
(a) Give a list of at least five radiations, in order of their increasing frequencies, which make up the complete electromagnetic spectrum.
(b) Which of the radiation mentioned by you in part (a) has the highest penetrating power.
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)X-rays,
What is the range of the wavelength of the following electromagnetic waves?
(A) Radio waves.
State the approximate range of wavelength associated with the ultraviolet rays.
The wavelength of X-rays is 0.01 Å. Calculate its frequency. State the assumption made, if any.
Which part of electromagnetic spectrum is used in radar systems?
Can X-rays be polarised?
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?
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.
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 wavelengths of Kα and Lα X-rays of a material are 21.3 pm and 141 pm respectively. Find the wavelength of Kβ X-ray of the material.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Name the scientist who discovered Ultraviolet rays
Name the part of the electromagnetic spectrum which is:
Produced by bombarding a metal target with high electrons.
Define the term "Intensity" in the photon picture of electromagnetic radiation.
Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each.
Give one use of electromagnetic radiation in Ultraviolet radiation.
Answer briefly.
Can we produce a pure electric or magnetic wave in space? Why?
What are the ultraviolet rays?
Answer briefly.
Give two uses of radio waves.
If the Earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.
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:
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:
Write two uses of the following radiation.
X-rays
Which one of the following electromagnetic radiation has the least wavelength?
Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.
Which description identifies how radio waves are mainly produced?
What can result from excess ultraviolet exposure?
Which properties characterize X-rays?
