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A : Optical and radio telescopes are bui...

A : Optical and radio telescopes are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth.
R : Atmosphere absorbs X-rays, while visible and radiowaves can penetrate it.

A

If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)

B

If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)

C

If assertion is true statement but Reason is false, then mark (3)

D

If both Assertion and Reason are false statements, then mark (4)

Text Solution

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The correct Answer is:
A
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The existence of negatively charged particle in an atom was shown by J.J. Thomson as a result of the studies of the passage of electricity through gases at extremely low pressure known as discharge tube experiments. When a high voltage of the order of 10,000 volts or more was impressed across the electrodes, some sort of invisible rays moved from the negative electrode to the positive electrode these rays are called as cathode rays. Cathode rays travel in straight path in absence of electrical and magnetic field . Cathode rays consist of material part and charged particles? Cathode rays produce X-rays and light is emitted when they strike on ZnS screen. Cathode rays penetrate through thin sheets of aluminium and other metals . They affect the photogenic plate and passes heating effect when they strike on metal foil. The raito of charge to mass i.e charge/mass is same for all the cathode rays irrespective of the gas used in the tube. The existence of positively charged particle in an atom was shown be E. Goldstein. He repeated the same discharge tube experiments by using a perforated cathode. It was observed that when a high potential difference was applied between the electrodes, not only cathode rays were produced but also a new type of rays were produced simultaneoulsy from anode moving towards cathode and passes through the holes or canal of the cathode. These termed as canal rays or anode rays. These rays travel in straight lines and consists of positively charged particles. These rays have kinetic energy and produces heating effect also. The e/m ratio of these rays is smaller than that of electrons. Unlike cathode rays, their e/m value is dependent upon the nature of the gas taken in the tube. These rays produced flashes of light on ZnS screen and can pass throughs thin metal foils. They can produce physical and chemical changes and are capable to produce ionisation in gases. For cathode rays the value of e/m:

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AAKASH INSTITUTE ENGLISH-ELECTROMAGNETIC WAVES-ASSIGNMENT SECTION - D Assertion-Reason Type Questions
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  4. A : If the earth did not have an atmosphere, its average surface temp...

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  5. A : It has been predicted that a global nuclear war on the earth would...

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  6. A : In an EM wave the magnitude of the electric field vector is more ...

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  7. A : The displacement current goes through the gap between the plates...

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  8. As the frequency of an ac circuit increases, the current first increas...

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  9. A : When cooking in microwave ovens, metal containers are used. R :...

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  10. A : Food is cooked faster by microwaves than by conventional gas burne...

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  11. A : Microwaves are commonly used in radar to locate flying objects. ...

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  12. A : Environmental damage has depleted the ozone layer in the atmosphe...

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  13. A: The electrical. Conductivity of the Earth's atmosphere does not cha...

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  14. A : Static crashes are heard on a radio when a lightening flash occurs...

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  15. A : TV signals are affected if a low flying aircraft passes by or a p...

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  16. A : Light waves can be polarised. R : All electromagnetic waves move...

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  17. A : In an electromagnetic wave the energy density in electric field ...

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  18. A : The poynting vector given as bar(S) = (bar(E ) xx bar( B))/(mu0) r...

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  19. A : The radiation pressure due to light waves is maximum when the sur...

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