Question Discussion & Solution

The relation among given numbers is that every number is the sum of the squares of the digits of the previous number:

936 → 9² + 3² + 6² = 81 + 9 + 36 = 126

126 → 1² + 2² + 6² = 1 + 4 + 36 = 41

41 → 4² + 1² = 16 + 1 = 17

17 → 1² + 7² = 1 + 49 = 50

50 → 5² + 0² = 25

25 → 2² + 5² = 4 + 25 = 29

All are mammal except Lizard.

The correct answer is Khejri.

Key Points
Khejri:

• It is known as Kalp Vriksha of desert.
• Prosopis cineraria is the scientific name.
• It was declared a state tree in the year 1983.
• It has a nitrogen-fixing tree which enhances the fertility of the soil.
• In 1988, the Indian Postal Department issued a Postal Stamp of paisa 60 on Khejri. 
• Khejri trees are found in the tropical thorny forest.

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.

Logic:

Train, Bus, and Boat are all vehicles,

Whereas a wheel is not a vehicle but a part of it.

Hence, "Wheel" is the odd word.