Defence
India's first liquid-mirror telescope is located in which state?
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Answer: Option C — Uttarakhand
Detailed Solution
India's first liquid-mirror telescope, the International Liquid Mirror Telescope (ILMT), was installed at the Devasthal Observatory, at a height of about 2,450 metres, near Nainital in Uttarakhand. It saw its "first light" (first observations) in 2022. It is also the first liquid-mirror telescope in Asia and the first one in the world built specially for astronomy.
About the ILMT:
- It is run by the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, an autonomous institute under the Department of Science and Technology.
- It was built in collaboration with scientists from Belgium and Canada.
- Its mirror is 4 metres in diameter.
How a liquid-mirror telescope works:
Instead of a solid glass mirror, it uses a pool of liquid mercury, a reflective metal that is liquid at room temperature.
The mercury is placed in a large dish that spins at a constant speed. The spinning makes the surface of the mercury take the shape of a perfect curve (a parabola), which can focus light like a normal telescope mirror.
A thin film of mylar protects the mercury from dust and wind.
Because the liquid must stay level, the telescope cannot be tilted. It always points straight up (at the zenith) and observes the strip of sky that passes overhead as the Earth rotates.
Uses: It surveys the sky every night to detect changing objects such as supernovae, gravitational lenses, space debris, asteroids and other "transient" objects.
Other telescopes at Devasthal:
The 3.6-metre Devasthal Optical Telescope (DOT), inaugurated in 2016 with Belgium's help, is the largest optical telescope in India.
Other important observatories in India:
- Indian Astronomical Observatory, Hanle (Ladakh): one of the highest observatories in the world; India's first Dark Sky Reserve was set up at Hanle in 2022.
- Vainu Bappu Observatory, Kavalur (Tamil Nadu).
- Mount Abu Infrared Observatory (Rajasthan).
- Giant Metrewave Radio Telescope (GMRT), near Pune.
Why not the other options?
- ✗Ladakh has the Hanle observatory and India's first Dark Sky Reserve.
- ✗Rajasthan has the Mount Abu Infrared Observatory.
- ✗Karnataka has the Gauribidanur radio observatory, but not the liquid-mirror telescope.
Quick tip
Remember: India's first liquid-mirror telescope (ILMT, 4 m, mercury) = Devasthal, Nainital (Uttarakhand), ARIES, 2022; largest optical telescope = 3.6 m DOT (also Devasthal); Dark Sky Reserve = Hanle.
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Firsts in India & World — Preparation
This question tests your understanding of Firsts in India & World, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers the first persons and events in India and the world: the first Indian to win a Nobel Prize, the first woman to hold major offices, the first to climb Everest or reach space, and India's first institutions, newspapers, railways and satellites. It also covers the largest, longest, highest and smallest records in India and the world. These are pure memory questions, so revise them as short lists by theme: first women, first in sports, first in science and space, and first in governance. Be careful with the exact wording, such as 'first Indian' versus 'first person of Indian origin', or 'first woman President' versus 'first woman Prime Minister', since options are often designed to exploit this. Practise the firsts in India and the world questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.