Question Discussion & Solution

The correct answer is 8 minutes.

• It takes 8 minutes to reach the earth.

Key Points

• Light is a form of energy which is propagated as electromagnetic waves.
• In the spectrum of electromagnetic waves, it lies between the ultra-violet and infra-red region and has a wavelength between 3900 Å to 7800 Å.
• light behaves as wave and particle both. 
• Speed of light is maximum in vacuum and air (3×10⁸ m/s).
• It is a transverse wave.
• It takes 8 min 19 s to reach on the earth from the sun.
• The light reflected from the moon takes 1.28 s  to reach earth.

Additional Information

• Electromagnetic waves are transverse, hence light is a transverse wave.
• Wave nature of light explains rectilinear propagation, reflection, refraction, interference, diffraction and polarization of light. 
• Refractive Index of a medium is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium. 
• Light is measured with two main alternative sets of units: radiometry consists of measurements of light power at all wavelengths, while photometry measures light with a wavelength.

The correct answer is Kalology.

Key Points

• The study of human beauty is called Kalology.
  • Kalology is the study of beauty and the ways in which beauty influences society.
  • This study is focused primarily on human attractiveness, rather than the broader field of aesthetics, and was popularized during the 19th century when philosophers attempted to codify beauty and create a uniform system for evaluating it.
  • A scale was even proposed, probably jokingly, which rated beauty in terms of the theoretical beauty of Helen of Troy, who allegedly had a face to launch 1,000 ships.

Additional Information

The correct answer is X-Ray.

• Electromagnetic (EM) radiation includes radiation via radio waves, microwaves, X-rays and gamma rays.

Key Points

• Electromagnetic (EM) radiation is a form of energy that is all around us and takes many forms.
• Electromagnetic (EM) radiation includes radiation via radio waves, microwaves, X-rays and gamma rays.
• Sunlight is also a form of EM energy.

​Additional Information

• ​EM radiation spans an includes a range of wavelengths and frequencies.
• This range is known as the electromagnetic spectrum.
• The EM spectrum is generally divided into seven regions:
  • Radio waves,
  • Microwaves,
  • Infrared (IR),
  • Visible light,
  • Ultraviolet (UV),
  • X-rays,
  • Gamma rays.

Important Points

• Radio waves have the longest wavelength.
• Gamma rays have the shortest wavelength.

The correct answer is Displacement.

Key Points

•  Displacement
  • When a body moves from one position to another, the shortest distance between the initial position and final position of the body along with direction is known as Displacement.
  • Its SI unit is a meter.
  • It is a vector quantity.
  • Displacement of the object can be positive, negative, zero.
  • Displacement of the object can never be greater than the distance traveled by it.
• When there is no change in an initial position and final position even after covering some path, then it is considered zero displacements.

Additional Information

• Distance
  • It is the actual path covered by a moving body irrespective of the direction in which the body travels.
  • Its SI unit is a meter.
  • It is a scalar quantity.
  • An odometer is used to measure the distance traveled by the vehicle.  
• Speed
  • The time rate of change of position of the object in any direction is called the speed of the object.
  • It is a scalar quantity.
  • Its SI unit is m/s.
  • Speed= Distance travelled/Time taken
• Frequency
  • It tells us how frequently an event occurs.
  • The number of complete waves produced in one second is called the frequency of the waves.
  • Hertz is the SI unit of Frequency. It is named in the honor of Rudolf Hertz.
  • 1 Hertz= 1 vibration per second.

The pattern followed is:

Hence, the correct answer is "72".