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NCERT Solutions Poorvi Chapter 5 Magnifying Glass — Let us explore

Book page 229 to 232 Updated on2026-09-05

Q1.
Children with low vision may benefit from different types of visual aids, such as magnifying spectacles, stand magnifiers, hand-held magnifiers, and telescopes. Magnifying spectacles are used for reading, threading a needle or doing other close-up tasks. Stand magnifiers rest above the object and are hands-free and help to keep the magnifying lens at a proper distance. Hand-held magnifiers with and without built-in lights, are usually smaller and lighter to move over printed material. They can be moved more easily. Telescopes are used to see objects or signs far away. Some telescopes can even be attached to eyeglasses.
Answer

This passage turns the poem's toy into a piece of medical equipment. Note the difference between low vision and blindness: a person with low vision has some usable sight that cannot be fully corrected by ordinary spectacles, so the aim of an aid is to make the remaining sight go further.

AidUsed forIts particular advantage
Magnifying spectaclesReading, threading a needle, close workBoth hands stay free; the lens is always at the right distance
Stand magnifierLong reading sessionsRests on the page and holds the exact focal distance — no shaking, no tiring arm
Hand-held magnifierPrices, labels, timetables, small print anywhereLight and portable; a built-in light helps in dim shops and corridors
Telescope (including spectacle-mounted)The blackboard, bus numbers, road signsBrings distant things close — the only one of the four that helps at a distance
The principle behind all four is the same as the poem's: the lens adds no information to the world; it enlarges the image falling on the retina so that whatever sight remains has more to work with. Which aid suits a person depends entirely on the distance of the task — near work needs magnifiers, distance work needs a telescope, and most low-vision users need both.
Find out and discuss: what your own school could do — seating a low-vision classmate in the front row, writing larger on the board with high contrast, providing large-print or audio textbooks (NCERT publishes them), and allowing extra time and a scribe in examinations, as the CBSE rules permit. In India these are entitlements under the Rights of Persons with Disabilities Act, 2016, not favours.
Q2.
Did you know that telescopes also use lenses? 1. The largest telescope in India for studying celestial objects is located in the district of Nainital, Uttarakhand. Commissioned in 2016, it is maintained and operated by ARIES (Āryabhaṭa Research Institute of Observational Sciences). 2. The Indian Astronomical Observatory (IAO) is a high-altitude astronomy station located in Hanle, Ladakh, India. It is situated at an elevation of 4,500 meters (14,764 ft), and supports optical, infrared, and gamma-ray telescopes. 3. The largest, most powerful, and most complex telescope ever launched into space is the James Webb Space Telescope. NASA launched it on, 25 December 2021. It orbits the Sun at a distance of 1.5 million kilometres from Earth. 4. The Mauna Kea Observatory, astronomical observatory in Hawaii, US, ... lies at an elevation of 4,205 metres (13,796 feet) atop the peak of Mauna Kea, a dormant volcano ... The observatories are set up here because of Mauna Kea’s high elevation, dry environment, and stable airflow that make it a prime location for astronomical observation. Find out more about them from the internet and discuss with your science teacher and classmates.
Answer
TelescopeWhereKey facts from the passage
Devasthal Optical Telescope (ARIES)Nainital district, UttarakhandIndia's largest for studying celestial objects; commissioned 2016; run by the Āryabhaṭa Research Institute of Observational Sciences
Indian Astronomical ObservatoryHanle, Ladakh4,500 m (14,764 ft); optical, infrared and gamma-ray telescopes
James Webb Space TelescopeIn orbit around the SunLargest and most complex ever launched; NASA, 25 December 2021; 1.5 million km from Earth
Mauna Kea ObservatoryHawaii, USA4,205 m (13,796 ft) on a dormant volcano; run by the University of Hawaii; hosts the Keck and Subaru telescopes
Read the four together and one question answers itself — why are observatories always in strange, uncomfortable places? A telescope's enemy is the atmosphere. So astronomers choose sites that give them as little of it as possible:
  • High — at 4,500 m in Hanle you are above roughly 40% of the atmosphere, and above most of its water vapour, which is what absorbs infrared light.
  • Dry — Ladakh is a cold desert and Mauna Kea sits above the cloud layer; water vapour blurs and absorbs.
  • Dark — far from city lights. Hanle is now a designated Dark Sky Reserve.
  • Steady air — “stable airflow” means less twinkling. Twinkling is charming to the naked eye and ruinous to a telescope.
And the James Webb telescope takes the argument to its conclusion: it removes the atmosphere entirely by leaving it, parking 1.5 million km away at the L2 point where Earth and Sun keep it permanently shaded, so its mirror can stay at about −233°C and detect faint infrared light.
Connect it to the poem: “Yes, and with lenses like it, / Eyeing the moon…” — de la Mare's speaker guessed that the same optics that magnify a scrap of chalk would reach the sky. Webb's mirror is 6.5 metres across and made of 18 gold-coated segments, but it is doing what the round glass in the poem does: gathering light and making the far-off legible.
Q3.
Read about ancient Indian scholars. 1. One of the eminent astronomers of the ancient India was Āryabhaṭa. His work Āryabhaṭiyam, laid the groundwork for various astronomers to develop in subsequent centuries and continues to be an important work even today. Āryabhaṭa proposed a heliocentric model of the solar system centuries before Copernicus. He also gave a scientific explanation of lunar and solar eclipses. 2. Varāmihira, the sixth-century CE astronomer, philosopher, and mathematician wrote the astronomical treatise Pañchasiddhāntika (Five Treatises), a compendium of Greek, Egyptian, Roman, and Indian astronomy. 3. The tenth-century CE mathematician-astronomer Bhāskarachārya II contributed significantly to the advancement of astronomical concepts. His works Siddhāntaśiromaṇi and Karaṇakutūhala, include compiled data on planetary positions, conjunctions, and eclipses.
Answer
ScholarPeriodChief workWhat he contributed
Āryabhaṭa5th century CEĀryabhaṭīyamExplained eclipses as shadows, not as a demon swallowing the Sun or Moon; held that the Earth rotates on its axis, which is why the stars appear to move; calculated π as 3.1416 and the length of the year with remarkable accuracy
Varāhamihira6th century CEPañchasiddhāntika (Five Treatises)Gathered Greek, Egyptian, Roman and Indian astronomy into one compendium — an early act of scientific comparison across cultures
Bhāskarāchārya II12th century CE (the passage says tenth)Siddhāntaśiromaṇi, KaraṇakutūhalaCompiled data on planetary positions, conjunctions and eclipses; his Līlāvatī is one of the most famous mathematical texts written in India
The unifying idea: all three were doing what this unit is about — replacing a story with an observation. Āryabhaṭa's account of eclipses is the clearest case: an eclipse had long been explained by the myth of Rahu and Ketu, and he said instead that the Moon passes into the Earth's shadow and the Moon's shadow falls on the Earth. That is exactly the shadow that freezes the air purifier in Feathered Friend — “one of our rare eclipses by Earth's shadow”.
Two points to check and correct as you research: (i) Bhāskarāchārya II belongs to the twelfth century CE (born 1114), not the tenth — the passage in the book is inaccurate here. (ii) Āryabhaṭa is often described as ‘heliocentric'; what his text clearly states is that the Earth rotates and that this rotation explains the apparent daily motion of the stars. Whether he also placed the Sun at the centre is debated by historians. Saying so precisely is better history than repeating the claim as settled.
Q4.
Jantar Mantar in New Delhi is an astronomical observatory. It has large-scale astronomical instruments designed for precise calculations and measurements of celestial movements. It was built in 1724 by Maharaja Sawai Jai Singh II. The observatory is a UNESCO World Heritage Site. Five such observatories were built by Jai Singh II, the other four are located in Ujjain, Mathura, Varanasi, and Jaipur.
Answer

The Jantar Mantar makes a striking point about instruments: it has no lenses at all. Jai Singh II found the small brass instruments of his day too imprecise, so instead of magnifying the sky he enlarged the instrument — some of these are the size of buildings, because a bigger scale means a finer reading.

InstrumentWhat it measures
Samrat YantraA giant sundial — a triangular gnomon with curved scales. The Jaipur one is about 27 m high and reads local time to roughly two seconds.
Jai Prakash YantraTwo hollow hemispheres, marked inside, in which the position of the Sun is read from where a crosswire's shadow falls — a map of the sky turned inside out.
Ram YantraCylindrical structures for measuring the altitude and azimuth of celestial bodies.
Misra YantraA composite of several instruments; it can indicate noon in cities in different parts of the world.

Where they are: Delhi (1724), and Jaipur, Ujjain, Mathura and Varanasi. The Jaipur Jantar Mantar is the one inscribed as a UNESCO World Heritage Site (2010); it is the largest and best preserved of the five.

Why they were built: Jai Singh needed accurate tables of planetary positions for calendars, for predicting eclipses and for astrological work at court. Accuracy in that era came from three things — size, permanence and careful alignment with the local latitude. His instruments are made of stone and marble and are fixed to the ground, so unlike a handheld astrolabe they never warp, wobble or need re-setting. That is the same engineering instinct behind a modern observatory: build it large, build it still, and put it where the conditions cannot spoil it.
If you visit: stand at the Samrat Yantra around midday and watch the shadow's edge move along the scale. You can see it travel — proof, with your own eyes, that the Earth is turning.
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