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प्रश्न
Answer briefly.
Give two uses of radio waves.
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उत्तर
- Radio waves are used for wireless communication purposes.
- They are used for radio broadcasting and transmission of TV signals.
- Cellular phones use radio waves to transmit voice communication in the ultra-high frequency (UHF) band.
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संबंधित प्रश्न
How are infrared waves produced?
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.
To which part of electromagnetic spectrum does a wave of frequency 3 × 1013 Hz belong?
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)].
If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?
A wave has wavelength 50 Å.
- Name the wave.
- State its speed in vacuum.
- State its one use.
Which radiation is used for satellite communication?
What is the range of the wavelength of the following electromagnetic waves?
(a) Visible.
State the approximate range of wavelength associated with infrared rays.
Name the radiations of wavelength just shorter than 4 × 10-7 m.
Give one use of microwaves.
Give one use of ultraviolet radiation.
In a Coolidge tube, electrons strike the target and stop inside it. Does the target get more and more negatively charged as time passes?
X-ray and visible light travel at the same speed in vacuum. Do they travel at the same speed in glass?
Can Lα X-ray of one material have shorter wavelength than Kα X-ray of another?
Frequencies of Kα X-rays of different materials are measured. Which one of the graphs in the figure may represent the relation between the frequency v and the atomic number Z ?
Cutoff wavelength of X-rays coming from a Coolidge tube depends on the
(a) target material
(b) accelerating voltage
(c) separation between the target and the filament
(d) temperature of the filament.
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.)
Find the maximum potential difference which may be applied across an X-ray tube with tungsten target without emitting any characteristic K or L X-ray. The energy levels of the tungsten atom with an electron knocked out are as follows.
| Cell containing vacancy | K | L | M |
| Energy in keV | 69.5 | 11.3 | 2.3 |
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.
Name the scientist who discovered Visible light
Name the scientist who discovered radio waves
Name three radiations and their wavelength range which are invisible and beyond the violet end of the visible spectrum.
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
Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each.
How will you investigate the existence of the radiation beyond the red and violet extremes of the spectrum?
Name two sources of ultraviolet radiation.
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?
Solve the numerical problem.
Calculate the wavelength in nm of an X-ray wave of frequency 2.0 × 1018 Hz.
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:
The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is ______.
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?
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.
In uranium (Z = 92) the K absorption edge is 0.107 Å and the Kα line is 0.126 Å, and the wavelength of the L absorption edge is ______.
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.
- Name one property common to both A and Radio waves.
What is the wavelength range of electromagnetic radiation used in radio broadcast?
