1. Edward Teller
2. Bernor Bon Bron
3. J. Robert Opan Heemar
4. Samual Cohen
Option “1” is correct. Edward Teller, one of the most famous scientists of 20th century was known as “father of hydrogen bomb”.
202. The time period of a pendulum-
1. Depends on the mass
2. Depends on the length
3. Depends on time
4. Depends on temperature
Option “2” is correct. The time period of a pendulum depends on its length. As we know that T = 2π√(l/g,) thus the result is that the one variable that affects the period of the pendulum is the length of the string. Increases in the length lead to increases in the period.
203. The rain drops are spherical because-
1. They fall from big height
2. The air has resistance
3. The water has surface tension
4. None of the above
Option “3” is correct. The rain drop spherical due to surface tension.
Option “2” is correct. The Sun produces energy by the nuclear fusion of hydrogen into helium in its core. Since there is a huge amount of hydrogen in the core, these atoms stick together and fuse into a helium atom. This energy is then radiated out from the core and moves across the solar system. This is the main source of energy for the sun and stars. Besides that the gravitational contraction in stars is also the source of their energy.
205. What is the source of electrical energy in an artificial satellite?
1. Solar cells
2. Mini nuclear reactor
3. Dynamo
4. Thermopile
Option “1” is correct. Solar (or photovoltaic) cells convert the sun’s energy into electrical energy through photoelectric effect. Photoelectric effect is the ability of matter to emit electrons when a light shines upon it.
206. A vast collection of stars held together by mutual gravitation is called-
1. A galaxy
2. Universe
3. Constellations
4. Nebula
Option “1” is correct. A vast collection of stars held together by mutual gravitation is called a Galaxy.
207. The stars which appear in the form of closed groups and form recognizable shapes and patterns are known as-
1. Supernova
2. Neutron stars
3. Milky Way
4. Constellations
Option “4” is correct. The stars which appear in the form of closed groups and form recognizable shapes and patterns are known as Constellations.
208. A cut diamond shines brilliantly due to-
1. Total internal reflection
2. Absorption of light
3. Some inherent property
4. Its molecular structure
Option “1” is correct. The refractive index of diamond is very high. Diamond achieves brilliance partially from total internal refraction. It has been cut or designed in such a way that if light enters into it, incident light strikes many of the internal surfaces.
209. Which of the following is used to take 3-dimentional pictures-
1. Photography
2. Holography
3. Radiography
4. None of the above
Option “2” is correct. Holography is a technique of producing a three-dimensional image of an object. Holography can work with sound, light or any wavelength. It is also been used for three-dimensional natural films.
210. An astronaut sees the colour of the sky as-
1. Blue
2. White
3. Black
4. Red
Option “3” is correct. The colour of the sky for an astronaut is black. It is because of the fact that in the space there is no atmosphere. Hence light doesn’t get scattered at all. In addition to this, in space, there are no air particles against which the sunlight can strike, get reflected or scattered. Hence, astronaut see everything black.
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