66th Prelims 2020

Explanation:

Infrared radiation is used for treating muscle aches as it provides deep heat to tissues, improving blood circulation and relieving stiffness. Microwaves are primarily used for cooking and communication, UV for sterilization and tanning, and X-rays for imaging.

Explanation:

Using the formula for parallel resistors: 1/RT = 1/R1 + 1/R2. Substituting RT = 1.403 kΩ and R1 = 2 kΩ gives 1/R2 = 1/1.403 - 1/2 ≈ 0.212, so R2 ≈ 4.72 kΩ.

Explanation:

In semiconductors, resistance decreases with increasing temperature because more charge carriers (electrons and holes) gain energy to move freely, enhancing conductivity. This is opposite to metals, where resistance typically increases with temperature.

Explanation:

Faraday constant (F) is universal and represents the electric charge carried by one mole of electrons. It does not depend on electrolyte amount, current, or solvent volume and is crucial for electrolysis calculations.

Explanation:

A light year is the distance light travels in one year in vacuum, approximately 9.46 trillion km. It is not a measure of time, speed, or intensity of light.

Explanation:

Electromagnetic waves, including light, travel at approximately 3 × 10^8 meters per second in vacuum. They consist of oscillating electric and magnetic fields and do not require a medium to propagate.

Explanation:

The frequency of light remains constant across different media. However, velocity, wavelength, and refractive index change depending on the medium.

Explanation:

Neil Armstrong was the first man to walk on the moon on July 20, 1969, during Apollo 11. Leonov performed the first spacewalk; Michael Collins stayed in the command module; Van Allen discovered Earth's radiation belts.

Explanation:

Number of neutrons = Mass number - Atomic number = 242 - 94 = 148.

Explanation:

Viscosity is resistance to flow. Among given options, honey is thickest and has highest viscosity. Air has the lowest, followed by water, then blood.

Explanation:

Milk provides calcium, protein, and carbohydrates but contains very little vitamin C, which is abundant in fruits and vegetables.

Explanation:

Zymase, a complex of enzymes in yeast, converts glucose to ethanol and CO2 during fermentation. Maltase splits maltose, invertase splits sucrose, and diastase (amylase) breaks down starch.

Explanation:

Breathalyzers use potassium dichromate-sulphuric acid. Alcohol oxidizes dichromate, causing a color change, indicating blood alcohol concentration.

Explanation:

CO2 reacts with calcium hydroxide (lime water) to form insoluble CaCO3, turning the solution milky.

Explanation:

Incomplete combustion produces CO due to insufficient oxygen. Complete combustion yields CO2.

Explanation:

pH is logarithmic. ΔpH = 3 means H+ concentration decreases by 10^3 = 1000 times.

Explanation:

Naphthalene sublimes, sand does not. Heating separates naphthalene vapor, which can be condensed back, leaving sand behind.

Explanation:

Benzene has 6 C-C sigma bonds + 6 C-H sigma bonds = 12 sigma; 3 double bonds contribute 3 pi bonds.

Explanation:

Urea (CO(NH2)2) contains Carbon, Hydrogen, Nitrogen, and Oxygen. Used as fertilizer, in protein synthesis, and skincare.

Explanation:

Lead has low thermal conductivity, making it a poor heat conductor. Copper is best, followed by zinc, mercury, then lead.

Explanation:

Vitamin K is essential for synthesizing proteins involved in coagulation, aiding blood clot formation.

Explanation:

Estrogen regulates female reproductive system and secondary sexual characteristics. Androgens are male hormones, insulin regulates glucose, oxytocin controls childbirth and lactation.

Explanation:

Arvid Carlson received the Nobel Prize for work on neurotransmission relevant to Parkinson's disease. Enders worked on polio, Laughlin on physics, Kohn on chemistry.

Explanation:

Iodine deficiency reduces thyroid hormone production, causing goiter. Vitamin A affects vision, calcium affects bones, iron affects hemoglobin.

Explanation:

Bitter taste receptors are concentrated at the back of the tongue. Sweet and salty are detected at the tip, sour at the sides.

Explanation:

Ginger has nodes and internodes, characteristic of stems. Roots lack nodes and internodes.

Explanation:

Fructose is sweeter than glucose, maltose, and sucrose. It is naturally found in fruits and honey.

Explanation:

Apple is a false fruit (accessory fruit) formed from ovary and other floral parts. Date, grape, and plum are true fruits from the ovary.

Explanation:

Legumes (beans, lentils, peas) are rich in protein, essential for tissue building and repair. They also contain fiber and minerals but protein is the key nutrient.

Explanation:

Cloves are harvested from unopened flower buds of Syzygium aromaticum, which are dried and used as a spice. Not from fruit, stem, or root.