Producers such as green plants absorb usable nitrogen compounds from the soil, including ammonia (NH₃) and nitrates. Nitrogen is essential for making proteins, chlorophyll, and nucleic acids necessary for plant growth and ecosystem balance.

Edward Jenner developed the first successful vaccine in 1796 by using cowpox material to protect against smallpox. His pioneering work laid the foundation of modern immunology and preventive medicine worldwide.

A camera lens forms a real, inverted, and usually diminished image on the film or image sensor. The lens focuses incoming light rays onto a surface, allowing the captured image to be recorded accurately for photography or digital imaging.

A standard mechanical stopwatch is commonly designed to measure time intervals as small as one-tenth of a second (0.1 sec). Such precision is useful in laboratories, sports timing, and scientific experiments requiring accurate measurements.

The devastating 1935 earthquake struck Quetta on 31 May 1935. It caused massive destruction and loss of life, making it one of the deadliest earthquakes in South Asian history and leading to improvements in building safety measures.