All questions of Physics for DSSSB TGT/PGT/PRT Exam

Activity.
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Statement Analysis:
Let's analyze each statement one by one:

Statement 1: It is developed by NASA.
Statement 2: It is used in NF-15B aircraft.
Statement 3: The IFCS Generation-I flight was first tested in 2003.
Statement 4: An artificial neural network is used in this control system.

Explanation:
Statement 1: It is developed by NASA.
The Intelligent Flight Control System (IFCS) is not specifically developed by NASA. It is a general term used to describe advanced flight control systems that incorporate intelligent algorithms and technologies.
Therefore, statement 1 is incorrect.

Statement 2: It is used in NF-15B aircraft.
The NF-15B aircraft is a modified version of the F-15B Eagle aircraft used for research and development purposes. It has been used by NASA and other organizations for various flight experiments and testing. While it is possible that an Intelligent Flight Control System (IFCS) could be used in the NF-15B aircraft, the statement does not provide enough information to confirm this.
Therefore, statement 2 is ambiguous and cannot be determined as correct or incorrect.

Statement 3: The IFCS Generation-I flight was first tested in 2003.
The statement mentions the testing of the IFCS Generation-I flight in 2003. However, there is no specific information available to confirm or refute this claim. Without any supporting evidence, we cannot determine the accuracy of this statement.
Therefore, statement 3 is ambiguous and cannot be determined as correct or incorrect.

Statement 4: An artificial neural network is used in this control system.
An artificial neural network (ANN) is a type of computational model inspired by the structure and functions of biological neural networks. ANNs have been widely used in various fields, including aerospace engineering, for tasks such as control systems, pattern recognition, and optimization. It is possible that an ANN could be used in an Intelligent Flight Control System (IFCS) to enhance its capabilities and performance.
Therefore, statement 4 is plausible and could be correct.

Conclusion:
Based on the analysis, statement 1 is incorrect, statement 2 and 3 are ambiguous, and statement 4 is plausible. Therefore, the correct answer is option 'C' - 1, 2, 3, and 4.

Understanding Elastic Limit
The elastic limit is a critical concept in materials science and mechanics, defining the threshold up to which a material can deform elastically. Beyond this limit, the material will not return to its original shape when the deforming force is removed.
Key Points about Elastic Limit:
- Definition: The elastic limit refers to the maximum stress or deforming force that a material can withstand while still returning to its original shape after the load is removed.
- Elastic Deformation: Within the elastic limit, materials exhibit elastic deformation, where they can stretch or compress without permanent changes in their structure.
- Plastic Deformation: Once the applied force exceeds the elastic limit, the material undergoes plastic deformation, meaning it will not return to its original shape, resulting in permanent changes.
Importance of Elastic Limit:
- Material Selection: Understanding the elastic limit is crucial for engineers and designers to select appropriate materials for specific applications, ensuring they can withstand loads without permanent deformation.
- Safety and Performance: Knowing the elastic limit helps in assessing the safety and performance of structures and components, preventing failure due to excessive stress.
Real-World Applications:
- Construction: In buildings and bridges, materials must be chosen based on their elastic limits to ensure they can support expected loads without undergoing irreversible deformation.
- Mechanical Components: Springs and other mechanical parts rely on their elastic properties, making it essential to operate within their elastic limits for effective functionality.
In summary, the elastic limit is the maximum force or stress a material can endure while retaining its elastic properties. Understanding this concept is vital for effective engineering and material science practices.

**Explanation:**

The correct answer is option **B) Distance**.

A light-year is a unit of distance used in astronomy to measure large distances in space. It is defined as the distance that light travels in one year in a vacuum. Since light travels at a constant speed of approximately 299,792 kilometers per second (or about 186,282 miles per second), the distance covered by light in one year is immense.

To better understand the concept of a light-year, let's break down the distance calculation and the significance of using this unit in astronomy:

**Definition of a Light-Year:**
- A light-year is the distance that light travels in one year.
- Light travels at a speed of about 299,792 kilometers per second (or about 186,282 miles per second).
- Therefore, in one year, light can travel about 9.46 trillion kilometers (or about 5.88 trillion miles).

**Importance of Light-Years in Astronomy:**
- The vast distances between celestial objects in space make it impractical to use conventional units like kilometers or miles.
- Astronomers use light-years to measure the distances between stars, galaxies, and other objects in the universe.
- Light-years allow us to comprehend the enormous scale of the universe and the time it takes for light to travel across such vast distances.

**Examples of Light-Years:**
- The nearest star to Earth, Proxima Centauri, is approximately 4.24 light-years away.
- The Andromeda Galaxy, our closest neighboring galaxy, is about 2.537 million light-years away.
- The observable universe is estimated to be about 93 billion light-years in diameter.

In conclusion, a light-year is a unit of distance used in astronomy to measure the vast distances between celestial objects. It represents the distance that light travels in one year and is an essential tool for understanding the scale and size of the universe.

Explanation:
A mirage is an optical illusion that occurs due to the bending of light rays. It is a phenomenon where distant objects appear to be shimmering, distorted, or displaced from their actual position. The correct answer is option 'D' because a mirage fits the description of an optical illusion.

Definition of a Mirage:
A mirage is a phenomenon that occurs when light rays bend due to the variation in air temperature. It usually happens in hot, desert-like environments where the ground is significantly heated. The bending of light causes an apparent displacement of objects, creating the illusion of water or reflections.

Causes of Mirage:
1. Temperature Gradient: Mirages occur due to the temperature gradient in the air. The air close to the ground is hotter than the air higher up. This temperature difference causes the light rays to bend as they pass through the layers of air with varying densities.

2. Total Internal Reflection: When light travels from one medium to another, it bends or refracts. In the case of a mirage, the temperature gradient causes the light rays to bend more than usual, leading to total internal reflection. This reflection creates the illusion of water or a shiny surface.

Types of Mirage:
1. Inferior Mirage: An inferior mirage is the most common type of mirage. It occurs when the air close to the ground is hotter than the air above. This causes the light rays to bend upwards, creating an image of objects below the actual position.

2. Superior Mirage: A superior mirage occurs when the air close to the ground is colder than the air above. In this case, the light rays bend downwards, creating an image of objects above their actual position. Superior mirages are often seen in cold Arctic regions.

Characteristics of a Mirage:
1. Shimmering Effect: Mirages create a shimmering effect, making the reflected image appear unstable or wavering.

2. Displacement: Mirages can displace the position of objects, making them appear higher or lower than their actual location.

3. Illusion of Water: One of the common characteristics of a mirage is the illusion of water. Due to the bending of light, distant objects may appear as if they are reflecting off a water surface.

4. Distance: Mirages often occur at a distance, particularly in desert areas where the ground is heated.

In conclusion, a mirage is an optical illusion that occurs due to the bending of light rays caused by a temperature gradient in the air. It creates the illusion of shimmering, displaced, or distorted objects, often resembling water or reflections.

Transition Metals Characteristics:
Transition metals have several unique characteristics that set them apart from other elements in the periodic table. One of the key characteristics of transition metals is their tendency to gain electrons. However, this is not a characteristic of transition metals. Let's explore the other characteristics in detail:

Low Electronegativity:
- Transition metals generally have low electronegativity compared to other elements. This means they have a lower tendency to attract electrons towards themselves in a chemical bond.

Low Ionization Energy:
- Transition metals have relatively low ionization energy, which is the energy required to remove an electron from an atom. This characteristic makes transition metals more likely to form positive ions.

Malleability:
- Transition metals are known for their malleability, which is the ability to be hammered or pressed into thin sheets without breaking. This property is due to the presence of delocalized electrons in the metal's structure.

Tendency to Gain Electrons:
- Unlike nonmetals, transition metals do not have a strong tendency to gain electrons. Instead, they typically lose electrons to form positively charged ions, which is a key characteristic of transition metals.
In conclusion, the correct answer is option 'A' - Tendency to gain electrons is not a characteristic of transition metals. Transition metals are known for their low electronegativity, low ionization energy, and malleability, making them unique elements in the periodic table.

Galvanizing: Protecting Iron from Rusting

Galvanizing is the method of protecting iron from rusting by coating it with a thin layer of zinc. It is a widely used technique to prevent corrosion and extend the lifespan of iron and steel objects. Let's delve into the details of galvanizing and why it is an effective method of protection.

1. What is Galvanizing?
Galvanizing is a process in which a layer of zinc is applied to the surface of iron or steel to create a protective barrier. The zinc coating acts as a sacrificial anode, meaning it corrodes instead of the iron or steel beneath it. This sacrificial action ensures that the iron or steel remains protected from rusting.

2. How is Galvanizing done?
The galvanizing process involves several steps:

2.1 Surface Preparation:
The surface of the iron or steel object is cleaned to remove any dirt, grease, or oxide layers. This step is crucial as it ensures proper adhesion of the zinc coating.

2.2 Immersion in a Zinc Bath:
The cleaned iron or steel object is immersed in a bath of molten zinc at a temperature of around 450°C. The object is carefully dipped into the bath, allowing the zinc to adhere to its surface.

2.3 Metallurgical Reaction:
During immersion, a metallurgical reaction occurs between the iron or steel and the molten zinc. This reaction forms a series of zinc-iron alloy layers on the surface of the object.

2.4 Cooling and Finishing:
After the object is removed from the zinc bath, it is allowed to cool, allowing the zinc coating to solidify and adhere firmly to the iron or steel surface. The galvanized object is then typically inspected for any defects or imperfections.

3. Advantages of Galvanizing:
Galvanizing offers several advantages as a method of protecting iron from rusting:

3.1 Corrosion Resistance:
The zinc coating provides excellent corrosion resistance to the iron or steel object, preventing rust formation even in harsh environments.

3.2 Longevity:
Galvanized objects have a longer lifespan compared to bare iron or steel. The zinc coating acts as a durable protective layer, extending the life of the object.

3.3 Cost-Effective:
Galvanizing is a cost-effective method of protection as it requires minimal maintenance. The initial investment in galvanizing pays off in terms of reduced repair and replacement costs.

3.4 Aesthetic Appeal:
Galvanized objects have a visually appealing silver-gray finish that is often desirable in architectural and decorative applications.

4. Applications of Galvanizing:
Galvanizing is widely used in various industries and applications, including:

- Construction: Galvanized steel is used in roofing, fencing, structural components, and other construction applications.
- Automotive: Galvanized parts are used in automobile manufacturing to enhance corrosion resistance.
- Agriculture: Galvanized equipment and structures are commonly used in farming and agricultural settings.
- Electrical: Galvanized electrical conduits and cable trays provide protection against corrosion.

In conclusion, galvanizing is a highly effective method of protecting iron from rusting by coating it with a thin layer of zinc. This process creates a barrier that prevents the iron

Explanation:

The correct answer is option 'A' which states that statements 1 and 2 are correct.

Statement 1: Dhanush missile is an indigenously developed naval version of the Prithvi short-range ballistic missile.

The first statement is correct. Dhanush missile is indeed an indigenously developed naval version of the Prithvi short-range ballistic missile. The Prithvi missile series was developed by the Defense Research and Development Organization (DRDO) of India, and the naval version of the missile is known as Dhanush. Dhanush is specifically designed for use by the Indian Navy and is capable of being launched from naval ships.

Statement 2: It is a single-stage missile and was developed by the DRDO, and it uses liquid propellant.

The second statement is also correct. Dhanush missile is a single-stage missile that was developed by the DRDO. It uses liquid propellant, which is a type of rocket propellant in liquid form. Liquid propellants are commonly used in missiles as they provide high energy density and are easier to handle and control during the launch.

Statement 3: It has a strike range of up to 350 km and can carry 500 kg of conventional warheads only.

The third statement is incorrect. Dhanush missile has a strike range of about 350 km, but it is capable of carrying different types of warheads, including both conventional and nuclear warheads. It has a payload capacity of around 500 kg, which allows for various types of warheads to be carried depending on the mission requirements.

Therefore, the correct answer is option 'A' as statements 1 and 2 are correct.

Understanding Laser Technology
Lasers are specialized devices that produce a specific type of light known as coherent light. Let's delve into why option 'B' is the correct answer.
What is Coherent Light?
- Coherent light consists of waves that are in phase with each other, meaning their peaks and troughs align perfectly.
- This results in a concentrated beam of light that can travel long distances without spreading out significantly.
Characteristics of Laser Light
- Monochromatic: Laser light is typically of a single wavelength, which means it appears as one color. This characteristic is essential in applications like laser surgery and optical communication.
- Highly Directional: Unlike ordinary light sources, lasers emit light in a narrow beam. This directionality allows for precise targeting, making lasers useful in various fields, including medicine and industry.
- High Intensity: The coherent nature of laser light means that it can achieve much higher intensities compared to regular light sources, allowing for powerful applications like cutting and engraving.
Why Not Other Options?
- A) Beam of White Light: White light is composed of multiple wavelengths and is not coherent.
- C) Microwaves: While microwaves are a form of electromagnetic radiation, they do not fall under the category of laser light.
- D) X-rays: X-ray production involves different mechanisms and does not produce coherent light as lasers do.
Conclusion
In summary, lasers are designed to produce coherent light, characterized by its monochromatic, directional, and intense properties, making option 'B' the correct answer. Understanding these features is crucial for grasping how lasers are utilized in various scientific and practical applications.

Explanation:

1. Each missile capable of carrying multiple warheads:
- MIRVs are designed to carry multiple independently targetable re-entry vehicles (MIRVs), which means that each missile can carry 2-10 separate nuclear warheads.
- This capability allows a single missile to target multiple locations or to overwhelm a missile defense system by releasing multiple warheads.

2. Warheads can be assigned to different targets:
- One of the key features of MIRVs is that each warhead can be assigned to a different target.
- This increases the flexibility and effectiveness of the missile system, as it can strike multiple targets simultaneously.

3. Multiple warheads can be assigned to the same target:
- While each warhead can be assigned to a different target, it is also possible for two or more warheads to be assigned to the same target.
- This redundancy ensures a higher probability of successful target destruction, even in the face of potential missile defense systems.

Therefore, all three statements are correct, making option 'D' the correct answer.

Explanation:
When two vectors are added, they can either give zero or a resultant vector. However, when three or more vectors are added, they can never give zero as the resultant vector. Let's understand why:

Two vectors:
When two vectors are added, they can either give zero or a resultant vector. If the two vectors are of the same magnitude and opposite in direction, they will give a resultant vector of zero. For example, if two forces of 5 N each are applied in opposite directions, they will cancel out each other and the net force will be zero.

Three vectors:
When three vectors are added, they can never give zero as the resultant vector. The reason is that three vectors can form a triangle, and the sum of any two sides of a triangle is always greater than the third side. Therefore, there will always be a resultant vector when three vectors are added.

Four or more vectors:
When four or more vectors are added, they can never give zero as the resultant vector. The reason is that four or more vectors can form a polygon, and the sum of any two sides of a polygon is always greater than the third side. Therefore, there will always be a resultant vector when four or more vectors are added.

Therefore, the minimum number of unequal vectors which can give zero resultant are two.

Ans.no.b