Q. Eclipses occur due to which optical phenomena -

Explanation by: Ram Sharma

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 Questions and Answers
4081.  The angle in which a cricket ball should be hit to travel max. horizontal distance is:

A
  60° with horizontal

B
 30° with horizontal

C
 15° with horizontal

D
 45° with horizontal

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Answer & Explanation
Answer : Option D
Explanation :
45° with horizontal.This has to do with the equation of a parabola or trajectory which is z = (tanq)x – q 2 (cos) q x 2. We can see that if the ball is fired at a 45 degree angle from the ground, the horizontal distance will be a maximum.
4082.  Which among the given is a radioactive element -

A
  Chromium

B
 Cobalt

C
 Uranium

D
 Argon


 
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Answer & Explanation
Answer : Option C
Explanation :
Uranium.Uranium (U) is a naturally occurring radioactive element. One of its isotopes, uranium-235, is the only naturally occurring isotope capable of sustaining a nuclear fission reaction. Its nucleus is unstable, so the element is in a constant state of decay, seeking a more stable ar- rangement.In fact, uranium was the element that made the discovery of radioactivity possible.
4083.  Synthetic detergents are prepared from

A
  glycerides

B
 potassium salts of higher fatty-acids

C
 hydrocarbons of petroleum

D
 sodium salts of higher fattyacids

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Answer & Explanation
Answer : Option C
Explanation :
hydrocarbons of petroleum.Synthetic detergents are prepared from hydrocarbons of petroleum. Calcium & magnesium salts of detergents are soluble in water. They are sodium salts of a long chain benzene sulphonic acids or sodium salts of long chain alkyl hydrogen sulphates. So cleansing action of detergents remain unaffected in hard water.
4084.  When Arsenic atoms are added to Germanium lattice, it becomes a/an

A
  Insulator

B
 Extrinsic semiconductor

C
 Intrinsic semiconductor

D
 Superconductor

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Answer & Explanation
Answer : Option B
Explanation :
When a pentavalent (donor) impurity, like arsenic, is added to germanium, it will form covalent bonds with the germanium atoms, leaving 1 electron relatively free in the crystal structure. Pure germanium may be converted into an N-type semiconductor by 'doping' it with any donor impurity having 5 valence electrons in its outer shell. Semiconductors which are doped in this manner - either with N- or P-type impurities - are referred toas EXTRINSIC semiconductors.
4085.  Ozone is

A
  Diamagnetic

B
 Paramagnetic

C
 Non-magnetic

D
 Ferromagnetic


 
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4086.  The tendency for complex formation is maximum in

A
  s-block elements

B
 p-block elements

C
 d-block elements

D
 noble gases

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Answer & Explanation
Answer : Option C
Explanation :
4087.  Mixture of which one of the following pairs of gases is the cause of occurrence of most of the explosions in mines?

A
  Hydrogen and oxygen

B
 Oxygen and acetylene

C
 Methane and air

D
 Carbon dioxide and methane

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Answer & Explanation
Answer : Option C
Explanation :
4088.  Which of the given is used as a catalyst in the production of high octane fuels -

A
  HCl

B
 HF

C
 H2 SO4

D
 HNO3


 
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Answer & Explanation
Answer : Option C
Explanation :
H2 SO4.Sulfuric acid is used as a catalyst for refining & for producing alkylate, an essential component of highoctane fuel. The hydrocarbon molecules are reformed into more complex molecules with a higher octane rating value.
4089.  Which of the following one of the following metals does not react with water to produce Hydrogen -

A
  Potassium

B
 Cadmium

C
 Lithium

D
 Sodium

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Answer & Explanation
Answer : Option B
Explanation :
Cadmium.Cadmium is a soft, malleable, ductile, bluish-white divalent metal. Unlike other metals, cadmium is resistant to corrosion & as a result it is used as a protective layer when deposited on other metals. It is similar in many respects to zinc but forms complex compounds. As a bulk metal, cadmium is insoluble in water & is not flammable; however, in its powdered form it may burn & release toxic fumes. Cadmium occurs as a minor component in most zinc ores & so is a byproduct of zinc production. It was used for a long time as a pigment & for corrosion resistant plating onsteel while cadmium compounds were used to stabilize plastic. With the exception of its use in nickel–cadmium batteries & cadmium telluride solar panels, the use of cadmium is generally decreasing. These declines have been due to competing technologies, cadmium's toxicity in certain forms & concentration & resulting regulations.
4090.  The unit of noise pollution (level) is:

A
  None of these

B
 decimal

C
 decibel

D
 ppm

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Answer & Explanation
Answer : Option C
Explanation :
decibel.Noise pollution refers to any unpleasant, damaging or irritating noise that has the potential to harm people, wildlife or the environment. A sound can also be measured by its pitch, which is the frequency of sound vibrations per 2nd. The decibel (dB) is the main unit used to measure the intensity or loudness of sounds.
4091.  What is used in storage batteries -

A
  Tin

B
 Lead

C
 Zinc

D
 Copper

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Answer & Explanation
Answer : Option B
Explanation :
Lead.The electrodes of the cells in a storage battery consist of lead grids. The openings of the cathodic grid is filled with lead dioxide (PbO2). The openings of the anodic grid is filled with spongy (porous) lead. Dilute sulfuric acid (H2 SO4) serves as the electrolyte.Leadacid batteries, alsoknown as lead storage batteries, can store a lot of charge & provide high current for short periods of time.
4092.  Eclipses occur due to which optical phenomena -

A
  Diffraction (FCI Assistant Grade-III Exam. 5.02.2013 (Paper-1)

B
 Reflection

C
 Refraction

D
 Rectilinear propagation

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Answer & Explanation
Answer : Option D
Explanation :
Rectilinear propagation.An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it & the viewer. This property applies to both transverse & longitudinal in addition an Electromagnetic wave. Rectilinear propagation is a wave property which states that waves propagate (move or spread out) in straight lines. Even though a wave front may be bent (the waves created by a rock hitting a pond) the individual waves are moving in straight lines.