Daily Quiz – 30th Apr 2024

Exp) Option c is the correct answer.

Statement I is correct: Turmeric stains on a cloth turn red when washed with soap. Turmeric is a natural indicator that turns red when it comes in contact with a base like soap. This is due to the presence of tartaric acid in turmeric and sodium hydroxide in soap, which react to produce a red color.

Statement II is incorrect: Soap solutions are not acidic; they are alkaline or basic. The alkaline nature of soap is a result of the presence of alkaline salts, such as sodium hydroxide or potassium hydroxide, in its composition. These alkaline substances give soap its cleansing properties. The pH

scale ranges from 0 to 14, with 7 considered neutral. Solutions with a pH below 7 are acidic, and those with a pH above 7 are basic. Most soaps have a pH above 7, making them basic.

Exp) Option b is the correct answer.

Mirages in deserts are primarily formed due to atmospheric total internal reflection caused by temperature gradients. On hot days, the lower air heats up more than higher layers, increasing the refractive index. The refractive index of air increases with its density. Hotter air is less dense and has a smaller refractive index than cooler air. If the air currents are small, that is, the air is still, the optical density at different layers of air increases with height.

Light from tall objects, like trees, traverses a medium with decreasing refractive index towards the ground. Consequently, the light undergoes successive bending and total internal reflection if the angle of incidence near the ground surpasses the critical angle. A distant observer perceives the light as emanating from below the ground, assuming it reflects off the ground, creating mirages—an optical illusion of inverted images of distant tall objects.

Exp) Option a is the correct answer.

Water is called the “universal solvent” because it is capable of dissolving more substances than any other liquid. This is important to every living thing on earth. It means that wherever water goes, either through the air, the ground, or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

It is water’s chemical composition and physical attributes that make it such an excellent solvent. Water molecules have a polar arrangement of oxygen and hydrogen atoms—one side (hydrogen) has a positive electrical charge, and the other side (oxygen) had a negative charge. This allows the water molecule to become attracted to many other different types of molecules.

Water can become so heavily attracted to a different compound, like salt (NaCl), that it can disrupt the attractive forces that hold the sodium and chloride in the salt compound together and, thus, dissolve it.

Exp) Option c is the correct answer.

Magnetism is a class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other.

Option 1 is correct: Electric motor uses a specific principle of magnetism, that is Principle of magnetic induction. The principle of magnetic induction states that, when a conductor moves through a magnetic field, or when a magnetic field changes around a conductor, an electric current is induced in the conductor.

The stator (the stationary part of the motor) generates a rotating magnetic field, inducing an electric current in the rotor (the rotating part of the motor). The interaction between the current-carrying rotor and magnetic field produces a force, creating torque and enabling rotational motion—a fundamental application of magnetism in motor operation.

Option 2 is correct: Credit card stripes uses the principles of electromagnetism, which combines electricity and magnetism, to store information. The stripe is made of a thin layer of iron oxide particles with a specific pattern, each acting as a tiny magnet. This pattern represents the card data like account number, expiry date, etc. When swiped through a card reader, the reader generates a magnetic field that interacts with the particles on the stripe. This interaction induces an electric current in the reader coil, varying based on the magnetization pattern. The reader analyzes the varying current to reconstruct the original magnetization pattern, thereby retrieving the encoded data.

Option 3 is incorrect: An acoustic guitar does not directly relate to the applications of magnetism in daily life. The sound in an acoustic guitar is produced by the vibration of strings and resonating body, not magnetism.

Option 4 is correct: Hard disk drives use magnetism in the process of storing and retrieving digital information. The data is recorded on magnetic disks.

Exp) Option b is the correct answer.

Optical Fiber refers to the technology that transmits information as light pulses along a glass or plastic fiber. A fiber optic cable can contain a varying number of glass fibers, from a few up to a couple hundred. These fibers can carry information, such as text, images, videos, telephone calls, and anything that can be encoded as digital information, across large distances almost at the speed of light.

Statement 1 is correct: Optical fibers work on the principle of total internal reflection of light. This means that when light enters the fiber, it is reflected back into the fiber instead of passing through it. This allows the light to travel long distances without significant loss of signal strength.

Statement 2 is correct: Optical fibers transmit high-speed data in the form of photons. The light signals are transmitted through the core of the fiber, which is surrounded by a cladding with a lower refractive index. The cladding ensures that the light signals remain confined within the core and do not escape through the sides of the fiber. This allows the signals to travel long distances without significant loss of signal strength.

Statement 3 is incorrect: Optical fibers cannot be used for long-distance electricity conduction. They are not suitable for transmitting electrical signals, which require a different type of cable. They are specifically designed for transmitting data using light signals, not electrical current.