A communications satellite in orbit send...

A communications satellite in orbit sends a parallel beam of signals down to earth. If these signals obey the same laws of reflections as light and are to be focussed onto a small receiveing aerial, what should be the best shape of the metal 'dish' used to collect them ?

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The correct Answer is:

Concave mital dish : It wil collect the parallel beam of satellite signals at its focus where raceiving aerial is fixed.

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Huygen was the figure scientist who proposed the idea of wave theory of light he said that the light propagates in form of wavelengths. A wavefront is a imaginary surface of every point of which waves are in the same. phase. For example the wavefront for a point source of light is collection of concentric spheres which have centre at the origin w_(1) is a wavefront w_(2) is another wavefront. The radius of the wavefront at time 't' is 'ct' in thic case where 'c' is the speed of light the direction of propagation of light is perpendicular to the surface of the wavelength. the wavefronts are plane wavefronts in case of a parallel beam of light. Huygen also said that every point of the wavefront acts as the source of secondary wavelets. The tangent drawn to all secondary wavelets at a time is the new wavefront at that time. The wavelets are to be considered only in the forward direction (i.e., the direction of propagation of light) and not in the reverse direction if a wavefront w_(1) and draw spheres of radius 'cDeltat' they are called secondary wavelets. Draw a surface w_(2) which is tangential to all these secondary wavelets w_(2) is the wavefront at time t+Deltat Huygen proved the laws of reflection and laws of refraction using concept of wavefront. Q. Spherical wavefronts shown in figure, strike a plane mirror. reflected wavefront will be as shown in

Huygen was the figure scientist who proposed the idea of wave theory of light he said that the light propagates in form of wavelengths. A wavefront is a imaginary surface of every point of which waves are in the same. phase. For example the wavefront for a point source of light is collection of concentric spheres which have centre at the origin w_(1) is a wavefront w_(2) is another wavefront. The radius of the wavefront at time 't' is 'ct' in thic case where 'c' is the speed of light the direction of propagation of light is perpendicular to the surface of the wavelength. the wavefronts are plane wavefronts in case of a parallel beam of light. Huygen also said that every point of the wavefront acts as the source of secondary wavelets. The tangent drawn to all secondary wavelets at a time is the new wavefront at that time. The wavelets are to be considered only in the forward direction (i.e., the direction of propagation of light) and not in the reverse direction if a wavefront w_(1) and draw spheres of radius 'cDeltat' they are called secondary wavelets. Draw a surface w_(2) which is tangential to all these secondary wavelets w_(2) is the wavefront at time t+Deltat Huygen proved the laws of reflection and laws of refraction using concept of wavefront. Q. Plane are incident on a spherical mirror as shown in the figure. the reflected wavefronts will be

Huygen was the figure scientist who proposed the idea of wave theory of light he said that the light propagates in form of wavelengths. A wavefront is a imaginary surface of every point of which waves are in the same. phase. For example the wavefront for a point source of light is collection of concentric spheres which have centre at the origin w_(1) is a wavefront w_(2) is another wavefront. The radius of the wavefront at time 't' is 'ct' in thic case where 'c' is the speed of light the direction of propagation of light is perpendicular to the surface of the wavelength. the wavefronts are plane wavefronts in case of a parallel beam of light. Huygen also said that every point of the wavefront acts as the source of secondary wavelets. The tangent drawn to all secondary wavelets at a time is the new wavefront at that time. The wavelets are to be considered only in the forward direction (i.e., the direction of propagation of light) and not in the reverse direction if a wavefront w_(1) and draw spheres of radius 'cDeltat' they are called secondary wavelets. Draw a surface w_(2) which is tangential to all these secondary wavelets w_(2) is the wavefront at time t+Deltat Huygen proved the laws of reflection and laws of refraction using concept of wavefront. Q. A point source of light is placed at origin, in air. the equation of wavefront of the wave at time t, emitted by source at t=0 is (take refractive index of air as 1)

Huygen was the figure scientist who proposed the idea of wave theory of light he said that the light propagates in form of wavelengths. A wavefront is a imaginary surface of every point of which waves are in the same. phase. For example the wavefront for a point source of light is collection of concentric spheres which have centre at the origin w_(1) is a wavefront w_(2) is another wavefront. The radius of the wavefront at time 't' is 'ct' in thic case where 'c' is the speed of light the direction of propagation of light is perpendicular to the surface of the wavelength. the wavefronts are plane wavefronts in case of a parallel beam of light. Huygen also said that every point of the wavefront acts as the source of secondary wavelets. The tangent drawn to all secondary wavelets at a time is the new wavefront at that time. The wavelets are to be considered only in the forward direction (i.e., the direction of propagation of light) and not in the reverse direction if a wavefront w_(1) and draw spheres of radius 'cDeltat' they are called secondary wavelets. Draw a surface w_(2) which is tangential to all these secondary wavelets w_(2) is the wavefront at time t+Deltat Huygen proved the laws of reflection and laws of refraction using concept of wavefront. Q. Certain plane wavefronts are shown in figure the refractive index of medius is

Huygen was the figure scientist who proposed the idea of wave theory of light he said that the light propagates in form of wavelengths. A wavefront is a imaginary surface of every point of which waves are in the same. phase. For example the wavefront for a point source of light is collection of concentric spheres which have centre at the origin w_(1) is a wavefront w_(2) is another wavefront. The radius of the wavefront at time 't' is 'ct' in thic case where 'c' is the speed of light the direction of propagation of light is perpendicular to the surface of the wavelength. the wavefronts are plane wavefronts in case of a parallel beam of light. Huygen also said that every point of the wavefront acts as the source of secondary wavelets. The tangent drawn to all secondary wavelets at a time is the new wavefront at that time. The wavelets are to be considered only in the forward direction (i.e., the direction of propagation of light) and not in the reverse direction if a wavefront w_(1) and draw spheres of radius 'cDeltat' they are called secondary wavelets. Draw a surface w_(2) which is tangential to all these secondary wavelets w_(2) is the wavefront at time t+Deltat Huygen proved the laws of reflection and laws of refraction using concept of wavefront. Q. Wavefronts incident on an interface between the media are shown in the figure. the refracted wavefront will be as shown in

What is the shape of the 'dish' of a dish antenna used for receiving TV signals from a satellite ?

Read the passage carefully and choose the best answer to each question out of the four alternatives. There may be some merit in this, but clearly, we need to look at the hawkers issue more broadly. For quite some time now, many middle-class citizens groups have urged strict action against hawkers, asking residents not to favour their business. The terms routinely used to refer to hawkers and vendors is “menace”, with their everyday businesses described as “encroachments” on public space. This, despite the fact that an existing 2014 central law, the Street Vendors (Protection of Livelihood and Regulation of Street Vending) Act, protects their presence as a part of the right to livelihood. The law specifies the number of licensed hawkers permitted and outlines the process to implement a fair street vending policy. Mumbai and other cities have failed to implement the law to date, with the Mumbai municipality having frozen hawker licenses since 1978. As a result, only a fraction of Mumbai’s hawkers are licensed. Hawkers desire legal status — their illegality makes them vulnerable to extortion and harassment by a whole range of State and non-State actors. Unfortunately, by looking upon the hawkers question as only a clearing of pavements issue, we have neglected to see their contribution in several other ways. Firstly, hawkers are not the only ones sullying our pavements. But they are far easier to target as villains than the middle-class who use pavements for car parking and shops/restaurants who unabashedly extend their shopfronts onto footpaths. Secondly, hawking is also an employment issue. It provides the urban poor a means to earn a legitimate livelihood, and in fact, many sell goods produced in small-scale or home-based industries. What makes the middle class too guilty of the same crime they blame hawkers?

LAKHMIR SINGH & MANJIT KAUR-REFLECTION OF LIGHT -Exercise

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