Question Discussion & Solution

Concept:

A functional dependency is a constraint between two sets of attributes from the database.

Explanation:

In general form, a functional dependency denoted by X -> Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuples that can form a relation state r of R.

The constraint is that for any two tuples T₁ and T₂ in r that have T₁[X] = T₂[Y], they must also have T₁[Y]

= T₂[Y]. It means that values of Y component of a tuple in r depend on or are determined by the value of X component.

If a relation R contains attributes (X and Y). Then X -> Y is a functional dependency. It means X functionally determines Y in R if and only if two tuples agree on their X value, they must necessarily agree on their Y value.

CONCEPT:

• Ultrasonic waves are the sound waves with frequencies higher than the upper audible limit of human hearing.
  • They have a short wavelength.
• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
  • Echoes are heard due to the phenomenon of Reflection of sound waves.
• SONAR: It a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water
  • SONAR stands for ‘Sound Navigation and Ranging.’
  • SONAR is based on the principle of echo.
  • Sonar is often used as a measurement of acoustic location and echo characteristics of the target object in the water.
  • It sends ultrasonic waves towards the bottom area of the sea and after reflection, the sound comes to the ship. We measure the time taken by the sound wave and then we get the depth. 

EXPLANATION:​

• From the above discussion, we can say that the SONAR uses the principle of reflection of sound waves(Echo) to detect and locate objects. So option 2 is correct.
• Reverberation: The persistence of sound in a closed enclosure, due to continuous reflections at the walls or the floor or the ceiling of the enclosure, even after the source has stopped producing sound is known as 'reverberation'.

Given: Sportspersons, Shooters, Swimmers

Logic: All shooters and swimmers are sportspersons but shooters and swimmers have no common relation.

Hence, option (2) is the correct answer.

All except 'Facebook' are name of search engine while 'Facebook' is the name of one of the social media.

The correct answer is 1024 megabytes

The size of information in the computer is measured in Kilobytes (KB), Megabytes (MB), Gigabytes (GB), and Terabytes (TB).

• 1 Kilobyte (KB) = about 1 thousand bytes (or 1024 bytes to be precise)
• One Megabyte (MB) is about 1 million bytes (or about 1024 Kilobytes (KB)).
• One Gigabyte (GB) is about 1 billion bytes, or (1024 Megabytes MB).
• One Terabyte (TB) is about roughly 1 trillion bytes or 1024 gigabytes (GB).