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Tv Signals Broadcast by a Delhi Studio Cannot Be Directly Received at Patna, Which is About 1000 Km Away.

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प्रश्न

TV signals broadcast by a Delhi studio cannot be directly received at Patna, which is about 1000 km away. But the same signal goes some 36000 km away to a satellite, gets reflected and is then received at Patna. Explain.

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उत्तर

To receive TV signals transmitted from Delhi in Patna directly, one has to use antennas of great height, which will cost much. On the other hand, transmission of signals with the help of satellites requires only high frequency waves and can be done easily.

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पाठ 17: Light Waves - Short Answers [पृष्ठ ३७९]

APPEARS IN

एचसी वर्मा Concepts of Physics Volume 1 and 2 [English]
पाठ 17 Light Waves
Short Answers | Q 5 | पृष्ठ ३७९

संबंधित प्रश्‍न

Draw the sketches to differentiate between plane wavefront and spherical wavefront.


Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of (a) reflected and (b) refracted light? Refractive index of water is 1.33.


The inverse square law of intensity \[\left(\text{i.e. the intensity }\infty \frac{1}{r^2}\right)\] is valid for a ____________ .


Which of the following properties of light conclusively support the wave theory of light?

(a) Light obeys the laws of reflection.

(b) Speed of light in water is smaller than its speed in vacuum.

(c) Light shows interference.

(d) Light shows photoelectric effect.


When light propagates in vacuum, there is an electric field as well as a magnetic field. These fields ____________ .

(a) are constant in time

(b) have zero average value

(c) are perpendicular to the direction of propagation of light.

(d) are mutually perpendicular


Three observers A, B and C measure the speed of light coming from a source to be νA, νBand νC. A moves towards the source and C moves away from the source at the same speed. B remains stationary. The surrounding space is water everywhere.

(a) \[\nu_A  >  \nu_B  >  \nu_C\]

(b) \[\nu_A  <  \nu_B  <  \nu_C\]

(c) \[\nu_A  =  \nu_B  =  \nu_C\]

(d) \[\nu_B  = \frac{1}{2}\left( \nu_A + \nu_C \right)\]


A parallel beam of light of wavelength 560 nm falls on a thin film of oil (refractive index = 1.4). What should be the minimum thickness of the film so that it strongly reflects the light?


A parallel beam of white light is incident normally on a water film 1.0 × 10−4 cm thick. Find the wavelengths in the visible range (400 nm − 700 nm) which are strongly transmitted by the film. Refractive index of water = 1.33.


A glass surface is coated by an oil film of uniform thickness 1.00 × 10−4 cm. The index of refraction of the oil is 1.25 and that of the glass is 1.50. Find the wavelengths of light in the visible region (400 nm − 750 nm) which are completely transmitted by the oil film under normal incidence.


Answer in brief:

In a double-slit arrangement, the slits are separated by a distance equal to 100 times the wavelength of the light passing through the slits.

  1. What is the angular separation in radians between the central maximum and an adjacent maximum?
  2. What is the distance between these maxima on a screen 50.0 cm from the slits?

White light consists of wavelengths from 400 nm to 700 nm. What will be the wavelength range seen when white light is passed through a glass of refractive index 1.55?


A parallel beam of green light of wavelength 550 nm passes through a slit of width 0.4 mm. The intensity pattern of the transmitted light is seen on a screen that is 40 cm away. What is the distance between the two first-order minima?


When light travels from an optically rarer medium to an optically denser medium, the speed decreases because of change in ______ 


What is the relation between phase difference and Optical path in terms of speed of light in a vacuum?


A Plane Wavefront of light of wavelength 5500 A.U. is incident on two slits in a screen perpendicular to the direction of light rays. If the total separation of 10 bright fringes on a screen 2 m away is 2 cm. Find the distance between the slits.


Light behaves as _________.


Emission and absorption is best described by ______.


Light emerges out of a convex lens when a source of light kept at its focus. The shape of wavefront of the light is ______.


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