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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
Why are microwaves considered suitable for radar systems used in aircraft navigation?
What role dose infra-red radiation play in physical therapy?
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.
Give a reason for the following:
It is necessary to use satellites for long-distance TV transmission. Why?
If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?
Why are infra-red waves often called heat waves? Explain.
State Moseley's law
State the approximate range of wavelength associated with infrared rays.
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.
Name two sources, each of infrared radiations and ultraviolet radiations.
The X-ray beam emerging from an X-ray tube
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.
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?
Iron emits Kα X-ray of energy 6.4 keV. Calculate the times taken by an iron Kα photon to cross through a distance of 3 km.
(Use Planck constant h = 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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.)
If the operating potential in an X-ray tube is increased by 1%, by what percentage does the cutoff wavelength decrease?
(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.)
State the name and the range of wavelength of the invisible electromagnetic waves beyond the red end of the visible spectrum.
Name the part of the electromagnetic spectrum which is:
Produced by bombarding a metal target with high electrons.
Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each.
State two properties of infrared radiations which differ from visible light.
Name the radiations used for the detection of fracture in bones.
What is the wavelength of the wave whose frequency is 1012 Hz? Name the electromagnetic wave.
Answer briefly.
Why light waves travel in a vacuum whereas sound waves cannot?
What are the ultraviolet rays?
Answer briefly.
Give two uses of ultraviolet rays.
Solve the numerical problem.
Calculate the frequency in MHz of a radio wave of wavelength 250 m. Remember that the speed of all EM waves in a vacuum is 3.0 × 108 m/s.
A bat moving at 10 ms−1 towards a wall sends a sound signal of 8000 Hz towards it. On reflection, it hears a sound of frequency f The value of f in Hz is close to (speed of sound = 320 ms−1)
The frequency of e. m waves which is best suited .to observed of radius 3 × 10–4 his of the order of
Ozone layer above the earth's atmosphere will
Radio waves of constant amplitude can be generated with.
Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.
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.
Assertion (A): Ultraviolet radiations is scattered more as compared to the microwave radiations.
Reason (R): Wavelength of ultraviolet radiation is more than the wavelength of microwave radiation.
Name two electromagnetic waves of wavelength smaller than that of violet light.
