Explanation: During photosynthesis, green plants use sunlight to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂). The oxygen gas released in this process comes specifically from the splitting of water molecules — a reaction known as photolysis of water, which occurs in the light-dependent reaction inside the chloroplasts.

Chemical equation:

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O

The oxygen atoms in the released O₂ come entirely from the original water molecules, as demonstrated by isotopic experiments using heavy oxygen (O¹⁸) tracers.

Explanation: A rainbow is formed due to the dispersion of sunlight into its constituent colors and total internal reflection inside water droplets in the atmosphere. The light entering a droplet is refracted, reflected internally, and then refracted again as it exits, producing the beautiful spectrum of colors.

Explanation: Mumps is a contagious viral disease caused by the mumps virus, a member of the Paramyxoviridae family (genus Rubulavirus). It primarily affects the salivary glands, especially the parotid glands, leading to painful swelling near the cheeks and jawline.

Mode of Transmission: The infection spreads through respiratory droplets or direct contact with saliva from an infected person.

Symptoms:

• Swelling and pain in the parotid glands (below the ears)
• Fever and headache
• Muscle pain and fatigue
• Difficulty in chewing or swallowing

Prevention: Mumps can be effectively prevented by the MMR vaccine (Measles, Mumps, and Rubella vaccine).

Explanation: Brass, an alloy of copper and zinc, gets discoloured when exposed to air containing hydrogen sulphide (H₂S). The H₂S reacts with the metal surface to form a dark layer of metal sulphides (mainly copper sulphide), causing tarnishing and loss of shine.

Explanation: Hardware refers to the physical components of a computer that can be seen and touched, such as the monitor, keyboard, mouse, CPU, and printer. In contrast, software consists of programs and instructions that control the hardware and perform tasks.

Explanation: Alternating current (AC) is used for long-distance transmission because energy losses are minimal. The voltage of AC can be easily increased or decreased using transformers, allowing transmission at high voltage and low current, which reduces power loss due to resistance in the wires.

Explanation: Entomology is a branch of Zoology that focuses on the study of insects, including their structure, classification, behavior, ecology, and evolution. Insects make up more than 75% of all known animal species on Earth and play crucial roles in pollination, decomposition, and food chains. Scientists who study insects are known as entomologists.

Explanation: An endoscope works on the principle of total internal reflection of light. It uses optical fibers to transmit light into the body and carry the reflected image back to the observer. This allows physicians to view internal organs without surgery.