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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 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?
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?
Name the phenomenon which shows the quantum nature of electromagnetic radiation.
State an additional use of the X-rays waves
Name the region beyond the violet end of the spectrum called.
Name the radiations of wavelength just longer than 8 × 10-7m.
Give one use of ultraviolet radiation.
Give one use of gamma rays.
Name the waves used for taking photographs in dark.
Name the waves of wavelength nearly 0.1 nm.
Name two sources, each of infrared radiations and ultraviolet radiations.
The wavelength of X-rays is 0.01 Å. Calculate its frequency. State the assumption made, if any.
Can a hydrogen atom emit characteristic X-rays?
An X-ray beam can be deflected
Consider a photon of a continuous X-ray coming from a Coolidge tube. Its energy comes from
If the current in the circuit for heating the filament is increased, the cutoff wavelength
50% of the X-ray coming from a Coolidge tube is able to pass through a 0.1 mm thick aluminium foil. The potential difference between the target and the filament is increased. The thickness of the aluminium foil that will allow 50% of the X-ray to pass through will be
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 cutoff wavelength for the continuous X-rays coming from an X-ray tube operating at 30 kV.
(Use Planck constant h = 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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.)
The electric current in an X-ray tube (from the target to the filament) operating at 40 kV is 10 mA. Assume that on an average, 1% of the total kinetic energy of the electron hitting hte target are converted into X-rays.
(a) What is the total power emitted as X-rays and (b) how much heat is produced in the target every second?
The short-wavelength limit shifts by 26 pm when the operating voltage in an X-ray tube is increased to 1.5 times the original value. What was the original value of the operating voltage?
(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 Visible light
Name the part of the electromagnetic spectrum which is:
Suitable for radar systems used in aircraft navigation.
Name the part of the electromagnetic spectrum which is:
Produced by bombarding a metal target with high electrons.
Calculate the shortest wavelength of electromagnetic radiation present in Balmer series of hydrogen spectrum.
Identify the part of the electromagnetic spectrum used in (i) radar and (ii) eye surgery. Write their frequency range.
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
State two properties of infrared radiations which differ from visible light.
Name the radiations used for the detection of fracture in bones.
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.
What is a carrier wave?
Which of the following is a tool used for separating the different color wavelengths from each other?
For television broadcasting, the frequency employed is normally
The frequency of x-rays, y-rays and ultraviolet rays are respectively a, b and c. Then:-
Following QN ∴ 14, the radiation force on the roof will be
The frequency of e. m waves which is best suited .to observed of radius 3 × 10–4 his of the order of
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?
Write two uses of the following radiation.
X-rays
Photons of an electromagnetic radiation has an energy 11 keV each. To which region of electromagnetic spectrum does it belong?
Choose the correct option related to wavelengths (λ) of different parts of the electromagnetic spectrum.
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.
Name the electromagnetic radiation whose frequency is 10 Hz.
What is the wavelength range of electromagnetic radiation used in radio broadcast?
Name two electromagnetic waves of wavelength smaller than that of violet light.
