Model Practice Test- 4 - UPSC MCQ

The correct option is A.
IR is a type of electromagnetic radiation, a continuum of frequencies produced when atoms absorb and then release energy. From highest to lowest frequency, electromagnetic radiation includes gamma-rays, X-rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.

Correct option is B

The Sun belongs to a galaxy called the Milky Way. Astronomers estimate there are about 100 thousand million stars in the Milky Way alone. Outside that, there are millions upon millions of other galaxies also!

A nebula is a giant cloud of dust and gas in space. Some nebulae (more than one nebula) come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form. A nebula is a giant cloud of dust and gas in space.

The periodicity and recurrence of eclipses is governed by the Saros cycle, a period of approximately 6,585.3 days (18 years 11 days 8 hours). It was known to the Chaldeans as a period when lunar eclipses seem to repeat themselves, but the cycle is applicable to solar eclipses as well.

Geodesy is the science of accurately measuring and understanding the Earth's geometric shape, orientation in space, and gravity field. Today, geodesists use space-based tools like the Global Positioning System (GPS) to measure points on the Earth's surface.

The correct option is C.
Solar measurements reveal that the average surface temperature of the sun is 6000° Celsius and that sunspots are about 1500° Celsius cooler than the area surrounding them (still very hot), and can last anywhere from a few hours to a few months.

D is the correct option. I, II and III are correct.
Statement IV is not correct as Accretion onto a black hole is the most efficient process for emitting energy from matter in the Universe, releasing up to 40% of the rest mass energy of the material falling in. 

Magnetic field on the tape.  Explanation: A tape is coated with tiny magnetic particles. These particles get magnetized, when electric signal passes through them. Thus, a tape recorder records sound in the form of magnetic field on the tape.

The correct option is Option C.

Qs shown in the fig angle of incidence in denser medium increases angle of refraction also increases. 
When angle of incidence equals the critical angle, the angle of refraction will be 90°. and if further increase in the incidence angle light undergoes reflection.
 

velocity of light in diamond=124000km/s
velocity of light in glass =200000km/s
velocity of light in water =225000km/s

Hence increasing order is diamond; glass and water.

Dioscorea deltoidea is known as India’s contraceptive plant. 
It is an endangered species belonging to family Dioscoreacea, It produce rhizomes or bulbils which is rich in sapogenin steroidal compounds. These compounds have immense medicinal, industrial and commercial importance. D. deltoidea is expectorant and sedative.