Explanation: Histology is the microscopic study of the structure of tissues. It involves examining thin slices of tissue under a microscope, often using special stains to highlight different cell parts. It is a crucial field in biology and medicine (pathology) for diagnosing diseases like cancer by looking for abnormal tissue changes.
42
Which gas is used in the purification of water?
✅ Correct Answer:Chlorine
Explanation: Chlorine is widely used for water purification and disinfection (chlorination). It effectively kills bacteria, viruses, and other parasites in drinking water and swimming pools. It is a powerful oxidant. While essential for public health, levels are carefully controlled to ensure the water remains safe to drink.
43
Who discovered the circulation of blood?
✅ Correct Answer:William Harvey
Explanation: William Harvey, an English physician, discovered the systemic circulation of blood in 1628. He was the first to demonstrate that the heart pumps blood around the body in a closed circuit involving arteries and veins. This debunked earlier theories that blood was consumed by the body and constantly regenerated.
44
Which vitamin is water-soluble?
✅ Correct Answer:Vitamin C
Explanation: Vitamin C (and Vitamin B complex) is water-soluble, meaning it dissolves in water and is not stored in the body. Excess amounts are excreted through urine, so they must be consumed daily through diet. In contrast, Vitamins A, D, E, and K are fat-soluble and can be stored in the body's fatty tissues.
45
The hardest substance available on Earth is:
✅ Correct Answer:Diamond
Explanation: Diamond is the hardest known natural substance. It is a crystalline form of pure carbon. Its atoms are arranged in a rigid lattice structure that gives it unmatched hardness. This property makes it not only valuable for jewelry but also essential for industrial cutting, drilling, and grinding tools.
46
Which mirror is used in the headlights of cars?
✅ Correct Answer:Concave Mirror
Explanation: A Concave Mirror is used in car headlights (and torches) because it can focus light into a powerful parallel beam. The bulb is placed at the focal point of the mirror. When light hits the curved surface, it reflects outward in straight lines, allowing the driver to see a long distance ahead in the dark.
47
What is the main cause of Acid Rain?
✅ Correct Answer:Sulfur Dioxide and Nitrogen Oxides
Explanation: Acid Rain is primarily caused by emissions of Sulfur Dioxide (SO2) and Nitrogen Oxides (NOx) from vehicles and factories. These gases react with water, oxygen, and other chemicals in the atmosphere to form sulfuric and nitric acids. This acidic rain damages forests, harms aquatic life in lakes, and erodes buildings and statues.
48
Which organ breaks down old Red Blood Cells?
✅ Correct Answer:Spleen
Explanation: The Spleen is known as the 'graveyard of red blood cells'. It acts as a blood filter. Old, damaged, or abnormal red blood cells are broken down and recycled here. The iron from the hemoglobin is saved for reuse, while the waste products are sent to the liver to be excreted as bile.
49
The chemical name of Plaster of Paris is:
✅ Correct Answer:Calcium Sulphate Hemihydrate
Explanation: Plaster of Paris is chemically Calcium Sulphate Hemihydrate (CaSO4·1/2H2O). It is made by heating gypsum to about 150°C. When mixed with water, it rehydrates and hardens quickly into a solid mass. It is widely used in medicine for setting broken bones (casts), in making sculptures, and in construction for false ceilings.
50
Which gas is used in refrigerators for cooling?
✅ Correct Answer:Ammonia / Freon
Explanation: Historically, Freon (CFCs) was used, but due to ozone depletion, modern refrigerators use Ammonia (in industrial settings) or HFCs (Tetrafluoroethane). These gases have a low boiling point. They circulate through the fridge's coils, absorbing heat from inside and releasing it outside, thereby keeping the interior cool.
51
Which device converts Mechanical Energy into Electrical Energy?
✅ Correct Answer:Generator (Dynamo)
Explanation: A Generator (or Dynamo) is a device that converts mechanical energy into electrical energy. It works on the principle of electromagnetic induction discovered by Michael Faraday. When a coil of wire rotates in a magnetic field (mechanical energy), it induces a flow of electric current. This is how power plants generate electricity.
52
Night Blindness is caused by the deficiency of:
✅ Correct Answer:Vitamin A
Explanation: Night Blindness (Nyctalopia) is the inability to see well at night or in poor light. It is most commonly caused by a deficiency of Vitamin A. Vitamin A is needed to make rhodopsin, a pigment in the eye's retina that detects low light levels. Without enough rhodopsin, the eyes cannot adapt to darkness.
53
What is the main component of Sand?
✅ Correct Answer:Silicon Dioxide (Silica)
Explanation: The most common constituent of sand is Silicon Dioxide (SiO2), commonly known as Silica, usually in the form of quartz. Sand is formed by the erosion of rocks over thousands of years. It is a primary raw material used in the manufacturing of glass and concrete. Deserts and beaches are covered with vast amounts of silica sand.
54
Which blood cells help in clotting?
✅ Correct Answer:Platelets
Explanation: Platelets (thrombocytes) are tiny blood cells that help your body form clots to stop bleeding. If one of your blood vessels gets damaged, it sends out signals to the platelets. The platelets then rush to the site of damage and form a plug (clot) to fix the damage. Low platelet count can lead to excessive bleeding.
55
The study of Insects is called:
✅ Correct Answer:Entomology
Explanation: Entomology is the scientific study of insects. Insects are the most diverse group of animals on Earth, with over a million described species. Entomologists study their classification, life cycles, behavior, and ecology. This field is crucial for agriculture (pest control), medicine (disease vectors like mosquitoes), and understanding biodiversity.
56
Which layer of atmosphere protects us from meteoroids?
✅ Correct Answer:Mesosphere
Explanation: The Mesosphere is the layer of the atmosphere directly above the stratosphere. It protects the Earth from meteoroids (space rocks). When meteors enter this layer, friction with the gas particles generates intense heat, causing most of them to burn up before they can reach the ground. We see these burning meteors as 'shooting stars'.
57
Who invented the World Wide Web (WWW)?
✅ Correct Answer:Tim Berners-Lee
Explanation: Sir Tim Berners-Lee, a British computer scientist, invented the World Wide Web in 1989 while working at CERN. He developed the first web browser, server, and website. His invention allowed documents to be linked together via hypertext over the internet, revolutionizing how information is shared globally.
58
Chemical name of Common Salt is:
✅ Correct Answer:Sodium Chloride
Explanation: Common Salt is chemically known as Sodium Chloride (NaCl). It is an ionic compound composed of sodium and chloride ions in a 1:1 ratio. It is essential for life, helping to regulate fluid balance and nerve transmission in the body. It has been used for thousands of years as a food preservative and seasoning.
59
Which gland produces Tears?
✅ Correct Answer:Lacrimal
Explanation: The Lacrimal Glands are responsible for producing tears. They are located above the outer corner of each eye. Tears are essential for keeping the eye moist, nourishing the cornea, and washing away dust and debris. They also contain enzymes like lysozyme that kill bacteria, protecting the eye from infection.
60
What is the unit of electric resistance?
✅ Correct Answer:Ohm
Explanation: The SI unit of electric resistance is the Ohm (symbol: Ω). It measures how much a material opposes the flow of electric current. It is named after Georg Ohm, a German physicist. According to Ohm's Law, Resistance = Voltage / Current. Materials with high resistance are insulators, while those with low resistance are conductors.