Advertisements
Advertisements
प्रश्न
Give a reason for the following:
It is necessary to use satellites for long-distance TV transmission. Why?
Advertisements
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
To which part of electromagnetic spectrum does a wave of frequency 3 × 1013 Hz belong?
A plane electromagnetic wave travels in the vacuum along the z-direction. What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is 30 MHz, what is its wavelength?
Name the phenomenon which shows the quantum nature of electromagnetic radiation.
Name the electromagnetic radiations used for (a) water purification, and (b) eye surgery.
Give the range of wavelength of the electromagnetic waves visible to us.
State the approximate range of wavelength associated with the ultraviolet rays.
State the approximate range of wavelength associated with visible light.
Give one use of gamma rays.
Name the waves used for taking photographs in dark.
Name of physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.
How are X-rays produced?
When a Coolidge tube is operated for some time it becomes hot. Where does the heat come from?
Can X-rays be polarised?
Can Lα X-ray of one material have shorter wavelength than Kα X-ray of another?
Consider a photon of a continuous X-ray coming from a Coolidge tube. Its energy comes from
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
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
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.
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.)
The Kα X-rays of aluminium (Z = 13) and zinc (Z = 30) have wavelengths 887 pm and 146 pm respectively. Use Moseley's law √v = a(Z − b) to find the wavelengths of the Kα X-ray of iron (Z = 26).
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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.
The wavelengths of Kα and Lα X-rays of a material are 21.3 pm and 141 pm respectively. Find the wavelength of Kβ X-ray of the material.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
When 40 kV is applied across an X-ray tube, X-ray is obtained with a maximum frequency of 9.7 × 1018 Hz. Calculate the value of Planck constant from these data.
(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 scientist who discovered Microwaves
Name the scientist who discovered Infra-red waves
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.
-
- 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.
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
Gamma rays and radio waves travel with the same velocity in free space. Distinguish between them in terms of their origin and the main application.
Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each.
Name the radiations used for the detection of fracture in bones.
Choose the correct option.
How does the frequency of a beam of ultraviolet light change when it travels from air into glass?
Answer briefly.
What are radio waves?
Answer briefly.
Name the most harmful radiation entering the Earth's atmosphere from outer space.
Answer briefly.
Why high-frequency carrier waves are used for the transmission of audio signals?
Solve the numerical problem.
Calculate the wavelength in nm of an X-ray wave of frequency 2.0 × 1018 Hz.
Name the e.m. waves which are suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves.
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)
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 frequency of e. m waves which is best suited .to observed of radius 3 × 10–4 his of the order of
The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is ______.
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?
What is the speed of radio waves in vacuum?
What happens when an electron collides with a positron?
