Question Discussion & Solution

The correct answer is Mirage.

• To a distant observer, the light appears to be coming from somewhere below the ground.
• The observer naturally assumes that light is being reflected from the ground, say, by a pool of water near the tall object.
• Such inverted images of distant tall objects cause an optical illusion to the observer.
• This phenomenon is called a mirage.
•  The optical illusion which occurs mainly in the desert during hot summer is based on the principle of TIR i.e total internal reflection.
• This type of mirage is especially common in hot deserts.

Additional Information

• Total Internal Reflection (TIR): When a ray of light goes from denser to the rarer medium it bends away from the normal and as the angle of incidence in denser medium increases, the angle of refraction in the rarer medium also increases and at a certain angle, angle of refraction becomes 90°, this angle of incidence is called critical angle (C).
• When the Angle of incidence exceeds the critical angle then the light ray comes back into the same medium after reflection from the interface. This phenomenon is called Total internal reflection (TIR).
• Conditions for TIR: 
  1. The ray must travel from denser medium to rarer medium.
  2. The angle of incidence 'i' must be greater than the critical angle C.

The correct answer is Its momentum is doubled.

Key Points

• Momentum is a vector quantity; it has both magnitude and direction.
• Isaac Newton’s second law of motion states that the time rate of change of momentum is equal to the force acting on the particle.
• Momentum can be calculated by multiplying the mass of an object by its forward velocity. (mv = kg*m/s).
• Mass and velocity are both directly proportional to the Momentum.
  • If you increase either mass or velocity, the Momentum of the object increases proportionally.
  • If you double the mass or velocity, you double the Momentum.
  • If you halve the mass or velocity, you half the Momentum.
• Newton's laws of motion-
  • ​Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force. This postulate is known as the law of inertia.
  • Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion. It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it. The momentum of a body is equal to the product of its mass and its velocity.
  • Newton’s third law states that when two bodies interact, they apply forces to one another equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.

Important Points

• Acceleration, the rate at which velocity changes with time in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down. Motion on a circle is accelerated even if the speed is constant because the direction is continually changing.
• Kinetic energy, a form of energy that an object or a particle has because of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and gains kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass.
• Potential energy, stored energy that depends upon the relative position of various parts of a system. Spring has more potential energy when it is compressed than stretched. A steel ball has more potential energy raised above the ground than it has after falling to Earth.

The correct answer is the stem.

Key Points

• Jute fibers are the bast fibers, generally soft and shiny.
• Jute is a natural fibre.
• Jute fiber consists of plant material cellulose and lignin.
• The jute fibrous are separated from the stem by using the following process: 
• The process includes three steps:
  • Retting
  • Stripping
  • Picking 
• Retting means soaked in water. In this process, the stem of jute plants is taken and made into bundles.
• These bundles are immersed in slow-running water, so the bundle gets wetted.
• Stripping process - In this process the non-fibrous thing is separated from the bundles. This process is done by hand.
• Picking process - After stripping the workers picked the fibrous from the mass of the stem. So, jute fiber is obtained from the stem of the jute plant. Hence, Option 4 is correct.
• The wetting process is of two types:
  • Ribbon wetting
  • Stem wetting After wetting the stripping process is done.

​ 

• Bast fibers are the fibers extracted from the past which surround the stem.
• Bast is also known as phloem.
• Jute is also called golden fiber due to its golden color and high economical value.
• It is a biodegradable and recyclable fiber. Jute fibers are used to make mats, twins and ropes, gunny sacks, and bags. Jute fiber has high tensile strength, smooth luster, and is silky and shiny.
• The main source of jute fibre is Corchorus olitorius.

The correct answer is Bookmark.

• A Chrome Internet browser, a method of saving web page addresses for quick access is Bookmark.

Key Points

• Bookmark
  • “Bookmark” refers to links to sites that we store for easy access later.
  • A bookmark is a saved shortcut that directs your browser to a specific webpage.
  • It stores the title, URL, and favicon of the corresponding page.
  • Saving bookmarks allows you to easily access your favourite locations on the Web.

Additional Information

• Proxy Setting
  • ​A proxy server acts as a gateway between you and the internet.
  • It’s an intermediary server separating end users from the websites they browse.
• Clear Cache
  • When we use a browser it saves some information from websites in its cache and cookies.
  • Clearing them fixes certain problems, like loading or formatting issues on sites.
• Delete history
  • Windows short cut to delete history:
    • CTRL+SHIFT+DEL

Concept-

• A cell is defined as the smallest unit of an organism with a nucleus.
• cells are made from the same major classes of organic molecules: nucleic acids, proteins, carbohydrates, and lipids.

• Example- a unit in the tissue of an animal muscle.

Key PointsParts of cell-

Cell membrane

• It is also called the plasma membrane,
• It is found in all cells and separates the interior of the cell from the outside environment.
• It is the outermost wall in the animal cell and placed next to the cell wall in the plant cell.
• Being an outer boundary of a cell, it provides shape to the cell.

Cell wall

• A cell wall is defined as the non-living component, covering the outmost layer of a cell.
• cell wall separates the interior contents of the cell from the exterior environment.
• It also provides shape, support, and protection to the cell and its organelles.

Nucleus

• A nucleus is defined as a double-membraned eukaryotic cell organelle that contains genetic material.
• It contains the cell’s hereditary information and controls the cell’s growth and reproduction
• It is responsible for coordinating many of the important cellular activities such as protein synthesis, cell division, growth, and a host of other important functions.

Ribosomes

• The ribosome is a complex molecule made of ribosomal RNA molecules and proteins that form a factory for protein synthesis in cells.

Additional Information  Cell was discovered by Robert Hooke in 1665, the cell has a rich and interesting history that has ultimately given way to many of today's scientific advancements.