CAPF (AC) 2021 (Paper-1) (Question 101-125)

• The method of estimating storm distance by counting the seconds between seeing lightning and hearing thunder is quite practical and widely used. It relies on the fact that sound travels at a speed that is easily perceptible over short distances and timescales,
  while light travels so fast that its travel time over the same distances is effectively instantaneous for practical purposes.
• The actual speed of sound in air can vary slightly depending on factors like temperature, humidity, and altitude. The value of 330 m/s is a common approximation for dry air at 0 °C. At higher temperatures, the speed of sound is slightly faster.
• This principle is not only useful for tracking thunderstorms but is also applied in other areas of physics and geophysics, such as in seismology to locate the epicenters of earthquakes by analyzing the arrival times of different types of seismic waves (P-waves and Swaves) which travel at different speeds through the Earth's crust.

The light which our eyes - our "remote sensors" - can detect is part of the visible spectrum. It is important to recognize how small the visible portion is relative to the rest of the spectrum. There is a lot of radiation around us which is "invisible" to our eyes, but can be detected by other remote sensing instruments and used to our advantage. The visible wavelengths cover a range from approximately 0.4 to 0.7 µm.

Electromagnetic wave is a collection of a different range of waves from radio to gamma electromagnetic waves. Microwaves and infrared waves can heat up food but does not make food “radioactive”. The waves cause vigorous vibration of molecules in food resulting in high temperature that cooks the food.

The properties of the image (real, inverted, and same size) give us crucial clues about the lens and the object/image positions:

• Real Image: A real image is formed when light rays actually converge at a point. Real images can be projected onto a screen. For a lens, real images are typically formed on the opposite side of the lens from the object.
• Inverted Image: An inverted image means the image is upside down relative to the object. Lenses that form real images always form inverted images.
• Same Size as Object: This means the magnification (ratio of image height to object height) is 1. However, since the image is inverted, the linear magnification mis

If objects in the distance appear blurry, it could be a sign that you suffer from short sightedness. Close-up vision is generally unaffected in people with myopia. However, in very severe cases of short sightedness, close-up vision can also become blurry.

Short sightedness may make it difficult to recognise faces at a distance, and driving can become more difficult too. In children, short sightedness can often be recognised when they have difficulty seeing the blackboard in their classroom, or watching television from a distance.

(A) Plants need rigid structure to support them as well as to defend themselves whereas, animals do not need any sort of cell wall since animals always move, they are not stationary in one particular place like plants, therefore they need to be flexible and as a result of that cell walls are absent.

(B) They are found in both animal and plant cells but are much larger in plant cells. Vacuoles might store food or any variety of nutrients a cell might need to survive. In plant cells, the vacuoles are much larger than in animal cells. When a plant cell has stopped growing, there is usually one very large vacuole.

(C) Presence of plastids is an exclusive character of plant cell. It contain chloroplast which is responsible for autotropic nature of plants. Since animals are heterotrophic, plastids are not found in animal cell.

Aerenchyma tissue containing enlarged gas spaces -occurs in many plants. It is formed either as part of normal development, or in response to stress (e.g. hypoxia). Two mechanisms of aerenchyma formation have been described; schizogeny, in which development results in the cell separation and lysigeny, in which cells die to create the gas space.

Smooth muscle (so-named because the cells do not have striations) is present in the walls of hollow organs like the urinary bladder, uterus, stomach, intestines, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive systems. These are not connective tissues.

Anabaena is a Cyanobacteria. These are unicellular prokaryotes that are placed under the kingdom Monera.

The genus Anabaena belongs to a class of cyanobacteria, which are known for their filamentous structure. These bacteria can form colonies of single cells or filamentous groups of cells. They are photosynthetic, and as a part of photosynthesis, they produce oxygen. Certain species of Anabaena are known to be effective natural fertilizers when used on rice fields.

Interestingly, some species of Anabaena produce neurotoxins, which are harmful to domestic animals, farm animals, and local wildlife. It is believed that the production of these neurotoxins aids in the symbiotic interactions of Anabaena, providing them with a defense mechanism against grazing stress.

Among the species of filamentous cyanobacteria is Anabaena variabilis. This photosynthetic prokaryote has the ability to fix atmospheric nitrogen gas and convert it into a form that can be utilized by plants. It can be found in a variety of aquatic environments including soil, freshwater, and saltwater. It forms either spherical or filamentous colonies.

As a nitrogen-fixing bacteria, Anabaena variabilis converts atmospheric nitrogen into a form that can be used by plants. This conversion is crucial as plants are unable to directly utilize nitrogen gas.

• HIV cannot be spread by sharing drinking glasses or through fine droplets coming out of mouth.
• No cases of HIV spread have ever been reported after a person has come in contact with the sweat, tears, urine, or feces of an HIV-infected person.
• The word AIDS stands for Acquired Immuno Deficiency Syndrome. This means deficiency of immune system, acquired during the lifetime of an individual indicating that it is not a congenital disease [disease or abnormality present from birth]. ‘Syndrome’ means a group of symptoms.
• AIDS was first reported in 1981 and in the last twenty-five years or so, it has spread all over the world.