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प्रश्न
Give a reason for the following:
It is necessary to use satellites for long-distance TV transmission. Why?
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उत्तर
- It is necessary to use satellites for long-distance TV transmissions because television signals are of high frequencies and high energies. Thus, these signals are not reflected by the ionosphere.
- Hence, satellites are helpful in reflecting TV signals. Also, they help in long-distance TV transmissions.
संबंधित प्रश्न
What role dose infra-red radiation play in maintain the Earth’s warmth
What role dose infra-red radiation play in physical therapy?
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1019 Hz belong?
What physical quantity is the same for X-rays of wavelength 10−10 m, red light of wavelength 6800 Å and radiowaves of wavelength 500 m?
If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?
Name the high energetic invisible electromagnetic waves which help in the study of the structure of crystals
What do you understand by the statement, "Electromagnetic waves transport momentum"?
Name the subjective property of light related to its wavelength.
(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.
What is the range of the wavelength of the following electromagnetic waves?
(A) Radio waves.
Give the range of wavelength of the electromagnetic waves visible to us.
What do you understand by the invisible spectrum?
Give one use of ultraviolet radiation.
Name the waves used for taking photographs in dark.
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.
Which part of electromagnetic spectrum is used in radar systems?
Can X-rays be used for photoelectric effect?
Characteristic X-rays may be used to identify the element from which they are being emitted. Can continuous X-rays be used for this purpose?
Can Lα X-ray of one material have shorter wavelength than Kα X-ray of another?
X-ray from a Coolidge tube is incident on a thin aluminium foil. The intensity of the X-ray transmitted by the foil is found to be I0. The heating current is increased to increase the temperature of the filament. The intensity of the X-ray transmitted by the foil will be
(a) zero
(b) < I0
(c) I0
(d) > I0
For harder X-rays,
(a) the wavelength is higher
(b) the intensity is higher
(c) the frequency is higher
(d) the photon energy is higher.
For a given material, the energy and wavelength of characteristic X-rays satisfy
(a) E(Kα) > E(Kβ) > E(Kγ)
(b) E(Mα) > E(Lα) > E(Kα)
(c) λ(Kα) > λ(Kβ) > λ(Kγ)
(d) λ(Mα) > λ(Lα) > λ(Kα).
The Kα and Kβ X-rays of molybdenum have wavelengths 0.71 A and 0.63 A respectively. Find the wavelength of Lα X-ray of molybdenum.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
The energy of a silver atom with a vacancy in K shell is 25.31 keV, in L shell is 3.56 keV and in M shell is 0.530 keV higher than the energy of the atom with no vacancy. Find the frequency of Kα, Kβ and Lα X-rays of silver.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
A free atom of iron emits Kα X-rays of energy 6.4 keV. Calculate the recoil kinetic energy of the atom. Mass of an iron atom = 9.3 × 10−26 kg.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Suppose a monochromatic X-ray beam of wavelength 100 pm is sent through a Young's double slit and the interference pattern is observed on a photographic plate placed 40 cm away from the slit. What should be the separation between the slits so that the successive maxima on the screen are separated by a distance of 0.1 mm?
Name the scientist who discovered Infra-red waves
-
- Calculate the speed of the wave.
- Name the medium through which it is traveling.
Define the term "Intensity" in the photon picture of electromagnetic radiation.
Name the radiation of the electromagnetic spectrum which is used for the following:
Radar and Give the frequency range.
Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each.
State two uses of infrared radiations.
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?
Answer briefly.
What are radio waves?
Answer briefly.
Give two uses of radio waves.
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:
Microwaves are electromagnetic waves with frequency in the range of.
The frequency of x-rays, y-rays and ultraviolet rays are respectively a, b and c. Then:-
If λv, λx and λm Am represents the wavelength of visible light, x-ray and microwaves respectively, then ______.
What happens to the intensity of light from a bulb if the distance from the bulb is doubled? As a laser beam travels across the length of a room, its intensity essentially remains constant. What geometrical characteristic of LASER beam is responsible for the constant intensity which is missing in the case of light from the bulb?
Write two uses of the following radiation.
Gamma rays
The half-value thickness of an absorber is defined as the thickness that will reduce exponentially the intensity of a beam of particles by a factor of 2. The half-value thickness in (µm) for lead assuming X-ray beam of wavelength 20 pm, µ = 50 cm-1 for X-rays in lead at wavelength λ = 20 pm, is ______ µm.
Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.
Name one radiation having the wavelength longer than the wavelength of these radiations.
What is the wavelength range of electromagnetic radiation used in radio broadcast?
