Question Discussion & Solution

The correct answer is A) 4, B) 2, C) 1, D) 3.

Key Points

• Sodium - It can be simply cut with knife as a result of Sodium has one negatron in its valence shell. Being the primary part of that amount, it is giant size.
• Mercury is liquid at temperature. A heavy, silvery d-block component, mercury is that the solely metal that's liquid at customary conditions for temperature and pressure.
• Silver is that the sensible conductor of electricity as a result of it contains the next variety of movable atoms (free electrons). For a fabric to be an honest conductor, the electricity more experienced it should be able to move the electrons.
• Lead being metal may be a dangerous conductor of electricity and warmth. Compared to alternative metals, lead may be a poor conductor of warmth whereas gold, silver, Pt square measure sensible conductors of warmth.

The correct answer is Amlanand Ghosh.

Key Points

• Prof Amlanand Ghosh excavated the Kalibangan site in 1952.
• The Kalibangan civilization is supposed to older than 4000 BC.
• This Rajasthan civilization was the first metropolis state in India.
• Kalibangan lies along with the left Bank of the dried-up bed of river Ghaggar.
• The site contains both pre-Harappan and Harappan remains, and therein can be seen the transition between the two cultures.
• Although the pre-Harappan culture worked copper and produced pottery, it had no writing system, and its ruins lack the orderly layout and use of baked brick that is found in the later Harappan sites.
• The Harappan remains include a cemetery and a fortified citadel. 

Additional Information

• Ratna Chandra Agrawal: 
  • Bhinmal Civilization was first founded by Ratna Chandra Agrawal in 1953-54 AD.
  • Bhinmal civilization is founded in the Jalore District of Rajasthan.
• Ratan Lal Mishra: 
  • Ganeshwar civilization was first founded in 1977 by historian Ratan Lal Mishra.
  • This Ganeshwar civilization is more than 4000 years old and the estimated time period was 2500 – 2000 BC.

The numbers are "2".

Hence, there are one such numbers.

Concept:

• Newton's Second Law of motion states that the rate of change of momentum of an object is proportional to the applied force in the direction of the force.
•  \(F = \frac{{dp}}{{dt}} = \frac{d}{{dt}}\left( {mv} \right)\;\left( \because {p = mv} \right)\) 

i.e., Force = ma ⇒ Force (F) ∝ a

Where,

F = the force applied, m = the mass of the body, a = the acceleration produced. p = linear momentum, v = velocity of particle at some instance

Explanation:

Given that;

Mass = 100 kg

Acceleration (a) = 10 m/s2

External force on body (F) = ma = 100 × 10 = 1000 N

The correct answer is to Correct the eye defects.

• Lenses are widely used in spectacle to correct eye defects.
• There are three common defects of vision that can be corrected with the help of suitable spherical lenses (convex lenses or concave lenses).
• Myopia is also known as Short-sightedness or nearsightedness.
  • Due to this defect, the person cannot see the distant objects clearly but he/she can see the nearby objects clearly.
  • The far point of the eye having myopia is less than infinity.
  • The defect is caused due to the high converging power of eye-lens or due to the eyeball being too long.
  • It can be corrected by making use of spectacles containing concave lenses.
• Hypermetropia is also known as Long-sightedness or farsightedness.
  • Due to this defect, the person cannot see the nearby objects clearly but he/she can see the distant objects clearly.
  • The near point of a hypermetropic eye is more than 25 centimetres away.
  • The defect is caused due to the low converging power of eye-lens or due to the eye-ball being too short.
  • It can be corrected by making use of spectacles containing convex lenses.
• Presbyopia is a vision disease caused mostly in old age.
  • The ciliary muscles become weak and the eye-lens become rigid and the eye loses its power of accommodation in old age in this vision defect.
  • In Presbyopia the person cannot see the nearby objects clearly due to loss of power of accommodation of the eye.
  • The near point of the old person having presbyopia gradually reduces and becomes much more than 25 centimetres away.
  • It can be corrected by making use of spectacles containing convex lenses.
• A person suffering from both Myopia and Hypermetropia uses spectacles having bifocal lenses in which the upper part consists of a concave lens to correct myopia and the lower part consists of a convex lens to correct hypermetropia.