Physics - Study Mode

[#1201] Light from the star, Alpha Centauri, which is nearest to the earth after the sun, reaches the earth in
Correct Answer

(C) 4.2 years

Explanation

Solution: Light from the nearest star reaches the earth in 4.2 years. The closest star to Earth are three stars in the Alpha Centauri system.

[#1202] Supersonic plane fly with the speed
Correct Answer

(C) greater than the speed of sound

Explanation

Solution: Vehicles that fly at supersonic speeds are flying faster than the speed of sound.

[#1203] Mach number is used in connection with the speed of
Correct Answer

(B) aircraft

Explanation

Solution: Mach number is used in connection with the speed of aircraft.

[#1204] On a stationary sail boat, air is blown from a fan attached to the boat. The boat
Correct Answer

(B) does not move

Explanation

Solution: In this case air blown by the fan will try to push the sail boat in a certain direction. But at the same time due to Newton's third law of motion the fan will experience a force due to the air blown in a direction opposite to the direction in which the sail boat will experience the force due to the blown air. So, as a whole the system will be at rest and it will not move.

[#1205] Rainbow is due to
Correct Answer

(D) refraction and reflection of sunlight by water droplets

Explanation

Solution: A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.