Martians planned to attack the Earth. The ruler of Mars, Think Tank instructed one of his Martian-Noodle to gather information about Earth. He saw that other three crew members-Captain Omega, Lieutenant Iota and Sergeant Oop found some books in Centerville Public Library. A book named 'Mother Goose' contained nursery rhymes. Omega managed to read some nursery rhymes like 'Mistress Mary', 'Humpty-Dumpty' etc. Think Tank completely misinterpreted the rhymes. He thought that Earthlings were intelligent enough in warfare and had advanced technology to grow high exposures. He was shocked to discover that metals could be grown in fields. On seeing the image of Humpty-Dumpty, he thought its head resembled that of his own. He feared invasion on Mars by the Earthlings. So instead of attacking the Earth, he decided to migrate one hundred million miles away from Mars to Alpha Centauri. Hence, the title 'The Book that Saved the Earth' is apt.

Photoelectric effect: When certain metals are exposed to a beam of light, the electrons are ejected from the metal. This phenomenon is called the photoelectric effect. The electrons ejected are called photoelectrons.

The results of this experiment were:

1. The electrons are ejected from the metal surface as soon as the beam of light strikes the surface, i.e., there is no time lag between the striking of the light beam and the ejection of electrons from the metal surface.
2. The number of electrons ejected is proportional to the intensity or brightness of the light.
3. For each metal; there is a minimum frequency, {tex}\nu_o{/tex} below which photoelectric effect is not observed.
4. K.E. of electrons {tex}\propto{/tex} frequency of light.

Equipment for studying the photoelectric effect. Light of a particular frequency strikes a clean metal surface inside a vacuum chamber. Electrons are ejected from the metal and are counted by a detector that measures their kinetic energy:

Explanation of photoelectric effect on the basis of quantum theory: When a photon of sufficient energy strikes an electron in the atom of the metal, it transfers its energy to the electron and the electron is ejected without delay. Greater the energy of the photon, greater will be the kinetic energy of the ejected electron.

The narrator noticed some of the family possessions missing at her home. Her mother informed her that Mrs. Dorling was taking these possessions to her home for safekeeping till the end of the war. She was initially apprehensive about the lady but the rebuking look from her mother was enough to drop the topic. Her first encounter with Mrs. Dorling was also a brief one and she could only catch a glimpse of her broad back.

1. 1. Due to greater electronegativity of sp² hybridised carbon to which carboxyl carbon is attached and greater resonance stabilization of carboxylate ion with the benzene ring, benzoic acid is a stronger acid than acetic acid.
   2. Methanal is more reactive towards nucleophilic addition reaction than ethanal because carbonyl carbon of methanal is more electrophilic than that of ethanol. Also, due to +I effect of methyl group in ethanal, reactivity of ethanal decreases.

इस कविता में कवि सुमित्रानंदन पंत जी ने पर्वतीय इलाके में वर्षा ऋतु का सजीव चित्रण किया है। पर्वतीय प्रदेश में वर्षा ऋतु होने से वहाँ प्रकृति में पल-पल बदलाव हो रहे हैं। कभी बादल छा जाने से मूसलधार बारिश हो रही थी तो कभी धूप निकल जाती है। दर्पण सा फैला है विशाल!

I have seen different type of houses in different areas like

1. Houses made up of wood, which are found in hilly areas.
2. Houses made up of wood, which are found in hilly areas.
3. Houses made up of cement, bricks, glass, etc. that are found in cities.

These houses are strong and can withstand heavy rains and storms, but the houses made up of mud and bamboo or of wood cannot withstand such climatic conditions.
  

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There are many legends related to the origins of tea. The Chinese legend about tea was that there was a Chinese emperor. He always boiled water before drinking it. One day, a few leaves of the twigs burning under the pot fell into the water and gave it a delicious flavour. It is said they were tea leaves.  

The keyboard is input device. The data which we want to feed into a computer may be typed on the keyboard in binary language. The other input devices are punched cards, paper tapes, magnetic tapes, magnetic discs, floppy discs, etc.

The purpose of the author's journey to Mount Kailash was to complete the Kora, which was a sacred religious ritual according to Hindu and Buddhist tradition.

Buying and selling of goods and services within the boundaries of a nation are referred to as internal trade. No custom duties or import duties are levied on such trade as goods are part of domestic production and are meant for domestic consumption. Internal trade can be categorised into two broad categories:

1. Wholesale trade
2. Retail trade

1. China has successfully focused on Pro-poor reforms.
2. Agrarian reforms have been effectively carried out.
3. Export driven manufacturing has significantly grown, adding to the pace of GDP growth.
4. SEZ policy has proved to be a boon for FDI flow in India.