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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
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1011 Hz belong?
Give a reason for the following:
Long-distance radio broadcasts use short-wave bands. Why?
State Moseley's law
Name the region beyond the red end of the spectrum.
Name the rays or waves of highest frequency .
Two waves A and B have wavelength 0.01 Å and 9000 Å respectively.
- Name the two waves.
- Compare the speeds of these waves when they travel in vacuum.
What are ultraviolet radiations?
Which part of electromagnetic spectrum is used in radar systems?
Can X-rays be polarised?
Consider a photon of a continuous X-ray coming from a Coolidge tube. Its energy comes from
If the potential difference applied to the tube is doubled and the separation between the filament and the target is also doubled, the cutoff wavelength
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?
50% of the X-rays coming from a Coolidge tube are able to pass through a 0.1 mm thick aluminium foil. If the potential difference between the target and the filament is increased, the fraction of the X-rays passing through the same foil will be
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.
Consider a photon of continuous X-ray and a photon of characteristic X-ray of the same wavelength. Which of the following is/are different for the two photons?
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 |
The electron beam in a colour TV is accelerated through 32 kV and then strikes the screen. What is the wavelength of the most energetic X-ray photon?
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
An X-ray tube operates at 40 kV. Suppose the electron converts 70% of its energy into a photon at each collision. Find the lowest there wavelengths emitted from the tube. Neglect the energy imparted to the atom with which the electron collides.
(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 radio waves
To which regions of the electromagnetic spectrum do the following wavelengths belong:
(a) 250 nm
(b) 1500 nm
Name the part of the electromagnetic spectrum which is:
Suitable for radar systems used in aircraft navigation.
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 two sources of infrared 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 light waves travel in a vacuum whereas sound waves cannot?
Answer briefly.
What is a carrier wave?
Light of wavelength `3500A` is incident on two metals A and B whose work functions are 3.2 eV and 1.9 eV respectively. Which metal will emit photoelectrons?
The fundamental frequency of an open organ pipe is 300 Hz. The first overtone of this pipe has same frequency as first overtone of a closed organ pipe. If speed of sound is 330 m/s, then the length of closed organ pipe is:
Electromagnetic waves with wavelength
- λ1 is suitable for radar systems used in aircraft navigation.
- λ2 is used to kill germs in water purifiers.
- λ3 is used to improve visibility in runways during fog and mist conditions.
Identify and name the part of the electromagnetic spectrum to which these radiations belong. Also arrange these wavelengths in ascending order of their magnitude.
Photons of an electromagnetic radiation has an energy 11 keV each. To which region of electromagnetic spectrum does it belong?
Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.
Name the electromagnetic radiation whose frequency is 10 Hz.
At what speed do all electromagnetic waves travel in a vacuum?
Where does infrared radiation lie relative to visible light?
Which set consists of applications of infrared radiation?
What can result from excess ultraviolet exposure?
Which set lists applications of X-rays?
