PGTRB:LATEST STUDY MATERIAL:
PHYSICS:
UNIVERSE:
- In the solar system eight planets along with their satellites revolve round the sun in elliptical orbits.
- Sun is the nearest star of earth.
- A large group of stars is called a galaxy.
- Kepler’s laws of planetary motion and Newton’s law of gravitational help us to study various physical properties as distance, period of revaluations size, mass, surface temperature and atmosphere of plants in solar system.
- Distance of a planet can be measured i)parallax method and ii)Kepler’s third law method.
- Presence or absence of the atmosphere on a plane is determined by using (i) the value of acceleration due to gravity and (ii) the average speed of the molecules.
- Solar system contains other objects also such as Asteroids, comets, meteors, and meteorites.
- A number of space probes have been conducted to know about the constituents of the solar system and to search for the possible existence of plant and animal life.
- Radio telescope is an astronomical instruments in astronomical research.
- Sun has been radiating energy at the rate of 4*10^ 26Js-1, as a result of nuclear fusion.
- By using Stefan-Boltzmann law surface temperature of the sun can be determined.
- There are three different types of stars: (i) Double and multiple stars. (ii) Intrinsically variable stars and (iii) Novae and super novae.
- A star is bam, lives for a certain length of time and eventually dies like everything else in the universe.
- The milky way is a large band of stars. There are about 150 billion stars in the milky way.
- Galaxies are classified into two broad categories, namely Normal Galaxies and Radio Galaxies.
- Normal Galaxies are further divided into three groups as spiral galaxies, irregular galaxies and elliptical galaxies based on their shape.
- Galactic clusters and Globular clusters are two types of star clusters.
- Hubble’s Law suggested that the universe is expanding.
- Three main theories account for the origin and evolution of the universe. (i) The big bang theory, (ii) the steady state theory and (iii) the pulsating theory.
- The branch of the science that deals with the study of universe is called Astronomy.
- Solar system is just a very small part of our galaxy called milky way.
- The dark lines in the absorption spectra lead to the identification of the gases present in the atmosphere of the planet.
- Jupiter reveals the presence of hydrogen, helium, methane, and ammonia gases.
- Clouds are good reflectors of light and hence if a planet is surrounded by clouds, its reflecting power will increase.
- Radio waves are fundamentally the same phenomenon as visible light, different only in wavelength.
- The solar constant can be determined by Phyroheliometer.
- The number of a satellites, that Jupiter has, is 12.
- Time taken by light to reach earth from the sun us 8 hrs 20 sec.
- Reflecting power of a heavenly body is called as Albedo.
- Temperature at the Centre of the sun is 14*10^6K.
- According to Hubble’s law V=HR.