Question Discussion & Solution

The correct answer is 4°C.

• Freezing of Water:
  • As water freezes, cold water (or ice formed) comes on the surface and warm water goes down.
  • Since the freezing temperature of the water is 0ºC or 273 K.
  • So water at the bottom should be at a higher temperature.
  • Water density at 4ºC is more than the density of water at 0ºC, hence the correct option is 4ºC.

​Key Points

• Reason of low temperature at bottom of the top layer:
  • This is due to the process of convection.
  • When the temperature of the water at the top layer reaches the freezing point, it is converted to ice.
  • But ice is lighter than water, so it will not sink to the bottom.
  • So there will be ice on the top surface and water would remain at the bottom of the lake. 

Stack

• It is a Last In First Out (LIFO) data structure
• Piles is another name used for stack since data element are placed one above the other and last element on the pile is the first one to be removed (LIFO)

• Push-down list: A list in which the next item to be removed is the item most recently stored (LIFO); Stack is a LIFO data structure
• The stack is used in situations where data have to be stored and then retrieved in reverse order.
• Real-life implementation of the stack is shown:

The ball which is stored last (D) will be the first one to be taken out of the container

Important Points

• Stacks data structures are also called FILO (first in last out)
• push(), pop(), peek() are some of the functions of stack data structure

The correct answer is Total Internal Reflection of Light.

Key Points

• Total Internal Reflection of Light
  • When a light ray, traveling from a denser medium towards a rarer medium is incident at the interface at an angle of incidence greater than the critical angle, then the rays are reflected back into the denser medium.
  • Practical Applications of Total Internal Reflection
  1. The working of optical fiber is based on total internal reflection.
  2. Mirage is formed due to total internal reflection.
  3. The brilliance of diamonds is mainly due to the total internal reflection of light inside them.

Additional Information

• Reflection of Light
  • The phenomenon of rebounding back of light rays in the same medium on striking a smooth surface is called reflection of light.
  • Silver metal is one of the best reflectors of light.
• Diffraction of Light
  • The phenomenon of bending of light around the corners and the spreading of light within the geometrical shadow of the opaque obstacles is called diffraction of light.
• Refraction of Light
  • Change in the path of a light ray as it passes from one medium to another is called refraction.

Explanation:

• Dynamite is an explosive which is used in mining, quarrying, construction and demolition industries. 
• It is made of Nitroglycerin, sorbents and stabilizers. 
• It was invented by Swedish Chemist Sir Alfred Nobel on whose memory the Nobel Prize has been constituted. 
• Nitro Glycerin: C3H5N3O9

The correct answer is Banas River.

• Banas River is known as "Forest's Hope".

Key Points

• Banas River
  • The Banas is a river that lies entirely within the state of Rajasthan.
  • It is a tributary of the Chambal River, itself a tributary of the Yamuna, which in turn merges into the Ganga.
  • Banas river originates in the Khamnor Hills of the Aravalli Range, near Kumbhalgarh in Rajsamand.
  • The name "Banaas" literally translates as "forest-hope" (Ban-aas) meaning "Hope-of-the-forest" or 'Van Ki Aasha.' 

Additional Information 

• Bedach River
  • The Berach River, a tributary of the Banas River.
• Bandi River
  • ​The Bandi is a tributary of the Luni River in the Pali district of Rajasthan state.
  • It merged in the Luni river in the Jodhpur district. 
• Arvari
  • ​The Arvari River is a small river flowing through the Alwar District of Rajasthan.