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Question 1 Report
A monochromatic light is one that
Answer Details
A monochromatic light is one that has a single wavelength or color. This means that it consists of light waves that all have the same frequency, resulting in a uniform appearance without any variation.
Question 2 Report
An effort of 40N is applied on a machine to lift a mass of 60kg. Determine the mechanical advantage of the machine [ g = 10ms2 ]
Answer Details
To determine the Mechanical Advantage (MA) of a machine, we use the formula:
MA = Load / Effort
Here, the Load is the weight of the mass being lifted, and the Effort is the force applied on the machine.
First, we need to calculate the Load. The Load is obtained by multiplying the mass of the object by the acceleration due to gravity (g = 10 m/s2).
So, the Load (weight of the mass) is:
Load = Mass × Gravity = 60 kg × 10 m/s2 = 600 N
The Effort given is 40 N.
Now, we can calculate the Mechanical Advantage:
MA = Load / Effort = 600 N / 40 N = 15
Therefore, the Mechanical Advantage of the machine is 15.
Question 3 Report
At a pressure of 105 Nm−2 , a gas has a volume of 20m3 . Calculate the volume at 4 x 105 Nm−2 at constant temperature.
Answer Details
In order to solve this problem, we can apply **Boyle's Law**, which states that the **pressure** and **volume** of a gas are inversely proportional at a constant temperature. Mathematically, this is expressed as:
P1V1 = P2V2
Where:
Rearranging the formula to solve for V2:
V2 = (P1V1) / P2
Substituting the given values:
V2 = (105 Nm-2 x 20 m3) / (4 x 105 Nm-2)
By calculating:
V2 = (2100 m3) / 4 x 105
V2 = 5 m3
Therefore, at a pressure of 4 x 105 Nm-2, the volume of the gas is 5 m3.
Question 4 Report
In voltage measurement, the potentiometer is preferred to voltmeter because it
Answer Details
In voltage measurement, a **potentiometer is preferred to a voltmeter** primarily because it **consumes negligible current**. Let me explain this in simpler terms:
A **voltmeter** is an instrument used to measure the potential difference (voltage) across two points in an electrical circuit. However, when a voltmeter is connected, it draws a small amount of current from the circuit to make the measurement, which can slightly alter the voltage being measured. This is particularly an issue in high-resistance circuits where even a small current draw can significantly affect the measurement.
On the other hand, a **potentiometer** is a device designed to measure voltage by comparing it with a known reference voltage without drawing current from the circuit under test. It comes into balance at a point where no current flows through it, ensuring that the measurement is not influenced by the potentiometer itself. This makes it a non-invasive method of measuring voltage, which is particularly useful for precise measurements in sensitive circuits.
Here’s a brief explanation about why the other options listed are less relevant:
Therefore, the key advantage of the potentiometer is its **ability to measure voltage without altering the circuit**, which stems from its negligible current consumption. This **ensures more accurate and reliable measurements** in many applications.
Question 5 Report
The dimension of power is
Answer Details
The dimension of power in physics is expressed in terms of the base units of mass (M), length (L), and time (T). Power is the rate at which work is done or energy is transferred over time, and it has the unit of watt (W) which is equivalent to one joule per second.
To derive the dimension of power:
1. Work has the dimension of energy, which is force applied over a distance. The dimension of work (or energy) is M L2 T-2 because force has the dimension M L T-2 and distance adds another L.
2. Since power is work done per unit time, you would divide the dimension of work by time (T).
Thus, the dimensional formula for power is:
M L2 T-3
Question 6 Report
What is the colour of red rose under a blue light?
Answer Details
To understand the color of a red rose under a blue light, we need to consider how we perceive color. Objects appear colored because they reflect certain wavelengths of light. A red rose appears red in white light because it reflects red wavelengths and absorbs others.
When you shine blue light on a red rose, the situation changes. A blue light primarily contains blue wavelengths. Since the red rose does not have red wavelengths to reflect anymore, and it cannot reflect blue light (as it absorbs it), the rose will appear to be the absence of any reflected wavelength visible to our eyes.
This means the rose will appear black under blue light, as black is perceived when no visible light is reflected into our eyes. Thus, the color of the red rose under a blue light is black.
Question 7 Report
The acceleration of a free fall due to gravity is not a constant everywhere on the Earth's surface because
Answer Details
The elliptical shape of the Earth: The Earth is not a perfect sphere; it is slightly flattened at the poles and bulging at the equator. This shape causes variations in gravitational acceleration.
Question 8 Report
If a body in linear motion changes from point P to Q, the motion is
Answer Details
When a body moves in a straight line from one point, such as point P, to another point, such as point Q, the motion is called Translational Motion. This kind of motion refers to an object moving along a path in which every part of the object takes the same path as a reference point. This means that if you follow any point on the body, it covers the same amount of distance in the same time frame as any other point.
Let's break down the other options:
In conclusion, since the body is moving from point P to point Q along a straight line, it exhibits Translational Motion.
Question 9 Report
A light ray passing from air into water at an angle of 30º from the normal in air would
Answer Details
When light passes from one medium to another, such as from air to water, it bends or refracts. This phenomenon is described by Snell's Law, which states: n₁ * sin(θ₁) = n₂ * sin(θ₂), where:
The refractive index of air is approximately 1, and the refractive index of water is approximately 1.33. Given the angle of incidence in air is 30º:
Using Snell's Law:
1 * sin(30º) = 1.33 * sin(θ₂)
You will find:
sin(θ₂) = sin(30º) / 1.33
sin(θ₂) ≈ 0.5 / 1.33
sin(θ₂) ≈ 0.375
Now, solve for θ₂ by taking the inverse sine (arcsin):
θ₂ ≈ arcsin(0.375)
θ₂ ≈ 22.09º
Thus, when a light ray passes from air into water at an angle of 30º from the normal in air, it will make an angle less than 30º from the normal in water, approximately 22.09º. This is because the light ray bends toward the normal as it enters a denser medium (water).
Question 10 Report
The gravitational force between two objects masses 1024 kg and 1027 kg is 6.67N. Calculate the distance between them [ G = 6.6 x 10−11 Nm2 kg−2 ]
Answer Details
To calculate the distance between two objects based on the gravitational force acting between them, we need to use the formula for gravitational force:
F = (G * m1 * m2) / r²
Where:
We need to compute r by rearranging the formula:
r² = (G * m1 * m2) / F
Therefore, the distance r is:
r = √((G * m1 * m2) / F)
Substitute the given values into the equation:
r = √((6.6 x 10-11 Nm²/kg² * 1024 kg * 1027 kg) / 6.67 N)
Calculating inside the square root:
G * m1 * m2 = 6.6 x 10-11 * 1024 * 1027 = 6.6 x 1040 Nm²
Then divide by the force:
6.6 x 1040 Nm² / 6.67 N = 0.99 x 1040 m²
Finally, calculate the square root:
r = √(0.99 x 1040)
r ≈ 1.0 x 1020 m
Therefore, the distance between the two objects is approximately 1.0 x 1020 m.
Question 11 Report
When thermal energy in a solid is increased, the change in state is called
Answer Details
When the thermal energy in a solid is increased, the solid particles gain energy and begin to vibrate more vigorously. As the temperature rises, these particles eventually have enough energy to overcome the forces holding them in their fixed positions. This leads to a change of state from a solid to a liquid. This process is known as melting.
To further understand this, imagine an ice cube. As it absorbs heat, it gains energy, and the ice (which is a solid) starts to turn into water (which is a liquid). This transition is what we refer to as melting.
Thus, the term that describes this change of state, when a solid is heated and turns into a liquid, is melting.
Question 12 Report
Answer Details
To solve this problem, we need to understand the relationship between pressure, volume, and temperature of a gas. The relevant law here is the **Combined Gas Law**, which is expressed as:
(P1 * V1) / T1 = (P2 * V2) / T2
Where:
In the given problem:
Applying the Combined Gas Law:
(P1 * V1) / 300 = (2 * P1 * V2) / 400
Simplifying this equation:
V1/300 = 2V2/400
Multiply both sides by 400 to clear the fraction:
400 * V1 / 300 = 2 * V2
Which further simplifies to:
(4/3) * V1 = 2 * V2
Dividing both sides by 2:
(2/3) * V1 = V2
This shows that the final volume, V2, is **2/3 of the initial volume, V1**. Therefore, the volume of the gas will **decrease by 1/3**.
Question 13 Report
Calculate the value of electric field intensity due to a charge of 4μC if the force due to the charge is 8N
Answer Details
To calculate the electric field intensity due to a charge, we need to use the formula:
Electric Field Intensity (E) = Force (F) / Charge (q)
In this problem, we are given that the force (F) is 8 Newtons (N) and the charge (q) is 4 microcoulombs (μC). First, we need to convert the charge from microcoulombs to coulombs:
1 microcoulomb (μC) = 1 x 10-6 coulombs (C)
Therefore, 4 μC = 4 x 10-6 C.
Now we can use the formula to find the electric field intensity:
E = F / q
E = 8 N / (4 x 10-6 C)
E = 8 / 4 x 106
E = 2 x 106
Thus, the value of the electric field intensity is 2 x 106 N/C.
Question 14 Report
An example of a non-rechargeable cell is
Answer Details
A non-rechargeable cell, commonly known as a primary cell, is a type of chemical battery that is designed to be used once until the chemical reactions that produce electricity are exhausted. After this point, the cell cannot be reversed or recharged.
In the given examples, the dry leclanche cell is a well-known example of a non-rechargeable cell. It is commonly used in everyday devices like remote controls, wall clocks, and torches. This cell type utilizes zinc and manganese dioxide as electrodes and relies on a moist paste of ammonium chloride for the electrolyte.
The other examples, such as nickel iron, mercury cadmium, and lead-acid, involve rechargeable cells (secondary cells) that are specifically designed to endure multiple charges and discharges throughout their useful life. Thus, unlike the dry leclanche cell, these can be recharged after use.
Therefore, the dry leclanche cell is an ideal example of a non-rechargeable cell because it can only be used once. After depletion, it cannot be recharged or reused.
Question 15 Report
Using the circuit above, at resonance
Answer Details
To understand the concept of resonance in an electrical circuit, it is crucial to know that resonance occurs when the inductive reactance and capacitive reactance are equal in magnitude. This typically happens in a series RLC (Resistor, Inductor, Capacitor) circuit. At resonance, the impedance of the circuit is purely resistive, meaning the circuit behaves as if it only contains a resistor. As a result, the voltages across the inductor and capacitor can be compared at resonance.
In this particular situation, the voltage across the inductor (VL) and the voltage across the capacitor (VC) are of interest due to their roles in resonance:
Thus, the correct expression of interest in relation to resonance is VL = VC, which indicates that the voltage across the inductor is equal in magnitude but opposite in phase to the voltage across the capacitor.
Question 16 Report
Calculate the quantity of heat for copper rod whose thermal capacity is 400Jk−1 for a temperature change of 60ºC to 80ºC
Answer Details
To calculate the quantity of heat absorbed or released by a substance, we can use the formula:
Q = C × ΔT
where:
Given:
First, calculate the change in temperature:
ΔT = Final temperature - Initial temperature = 80°C - 60°C = 20°C
Now, substitute the values into the formula to find the quantity of heat:
Q = 400 J/°C × 20°C
Calculate the answer:
Q = 8000 J
Since the options provided are in kilojoules (KJ), we need to convert joules (J) to kilojoules (1 KJ = 1000 J):
Q = 8000 J ÷ 1000 = 8 KJ
Therefore, the quantity of heat for the copper rod, given the specified conditions, is 8 KJ.
Question 17 Report
The total number of ATP produced during glycolysis is
Answer Details
During the process of glycolysis, a single glucose molecule is broken down into two molecules of pyruvate. During this metabolic pathway, there is a net gain of adenosine triphosphate (ATP) molecules. To understand how many ATP molecules are produced, let's break it down step by step.
1. **Initial ATP Investment:** Glycolysis initially requires an investment of 2 ATP molecules to phosphorylate glucose and convert it into a more reactive form during the early stages of the glycolytic pathway.
2. **ATP Production:** As glycolysis progresses, a total of 4 ATP molecules are produced. This occurs in the later steps of the pathway where adenosine diphosphate (ADP) is phosphorylated to form ATP. This is known as substrate-level phosphorylation.
3. **Net ATP Gain:** To find out the net gain of ATP through glycolysis, simply subtract the initial ATP investment from the total ATP produced:
Net ATP = Total ATP produced - Initial ATP investment
Net ATP = 4 ATP - 2 ATP
Net ATP = 2 ATP
Thus, the net total number of ATP produced during glycolysis is 2 molecules.
Question 18 Report
The land and sea breeze is attributed to
Answer Details
The phenomenon of land and sea breeze is primarily attributed to convection.
To understand this, let's first look at what land and sea breezes are:
Land Breeze: At night, the land cools down faster than the sea. The cooler, denser air from the land moves towards the sea, and this is known as a land breeze.
Sea Breeze: During the day, the land heats up more quickly than the sea. The warmer, lighter air over the land rises, and the cooler air from the sea moves in to take its place. This movement of air from the sea to the land is known as a sea breeze.
Both of these processes involve the movement of air due to differences in temperature and density, which is essentially the process of convection.
Convection is the transfer of heat through a fluid (like air or water) and is responsible for moving air masses and creating these breezes. The warm air, being less dense, rises, and the cooler, denser air moves in to replace it.
In contrast, conduction is the transfer of heat through a solid material, and radiation is the transfer of heat in the form of electromagnetic waves, neither of which primarily drive the processes of these breezes, making convection the key player.
Question 19 Report
Which of the following is not a part of model rocket?
Answer Details
When it comes to a model rocket, it is crucial to understand the different parts that make up the rocket and their functions:
Now, “Not recovery devices” is listed among the options. A recovery device is actually a part of a model rocket system. Common recovery devices include parachutes or streamers that deploy after the rocket reaches its peak altitude, allowing it to return safely to the ground. Such devices are indeed part of a model rocket design.
Therefore, the option “Not recovery devices” itself is not recognized as a part of a model rocket. Instead, the sentence is stating that they are not part of the main components, which implies it's indicative rather than being the name of a component. Hence, it does not pertain to a single component like the body tube, nose cone, or fins.
Question 20 Report
What will be the weight of a man of mass 60kg standing in a lift if the lift is descending vertically at 3ms2 ?
Answer Details
To find the apparent weight of a man of mass 60 kg standing in a descending lift, we first need to understand the concept of apparent weight. Apparent weight is the force that the man feels as his weight due to the reaction of the lift floor on him. When the lift accelerates, the apparent weight changes from his actual weight.
In this case, the lift is descending with a constant velocity of 3 m/s2. Since the acceleration is downward, it means the lift is accelerating negatively compared to an upward acceleration.
The formula to find the apparent weight (Wapparent) when in a lift is:
Wapparent = m(g - a)
Where:
Substituting these values into the formula, we get:
Wapparent = 60 (9.8 - 3)
Calculating further:
Wapparent = 60 × 6.8
Wapparent = 408 N
The closest option to 408 N in the answers provided is 420 N. Therefore, the correct answer is 420 N.
Question 21 Report
Newton's law of cooling is valid only for a
Answer Details
Newton's Law of Cooling states that the rate of heat loss of an object is directly proportional to the difference in temperature between the object and its surroundings, provided that this temperature difference is small.
Therefore, this law is only valid within a small temperature range.
Question 22 Report
A solid cube of aluminum is 1.5cm on each edge. The density of aluminum is 2700kgm−1 . Find the mass of the cube.
Answer Details
The mass of an object can be calculated using the formula:
Mass = Density × Volume
In this case, we need to find the mass of a solid cube of aluminum. Given:
First, we need to calculate the volume of the cube. The volume V of a cube with edge length a is given by:
V = a3
Substitute the edge length:
V = (1.5 cm)3 = 1.5 × 1.5 × 1.5 cm3 = 3.375 cm3
Since the density is given in kg/m3, we should convert the volume from cm3 to m3. There are 1,000,000 cm3 in 1 m3, so:
Volume in m3 = 3.375 cm3 × (1 m3/1,000,000 cm3) = 3.375 × 10-6 m3
Now, use the mass formula:
Mass = Density × Volume
Mass = 2700 kg/m3 × 3.375 × 10-6 m3
This equals:
Mass = 9.1125 × 10-3 kg
Convert kg to grams (since 1 kg = 1000 g):
Mass = 9.1125 grams
So, the mass of the cube is approximately 9.1 g. Thus, the correct answer is 9.1 g.
Question 23 Report
The moon's acceleration due to gravity is 16 of the earth's value. The weight of a bowling ball on the moon would be
Answer Details
To determine the weight of a bowling ball on the moon, we need to understand the relationship between weight, gravity, and mass.
Weight is the force exerted by gravity on an object. On Earth, this force depends on the object's mass and the acceleration due to gravity, which is approximately 9.8 m/s². Weight can be calculated using the formula:
Weight = Mass x Gravity
On the moon, the acceleration due to gravity is only 1/6 of Earth’s gravity. This means the gravitational pull on the moon is much weaker compared to the Earth. If we take the Earth's gravity to be 9.8 m/s², the moon's gravity would be:
Moon's Gravity = (9.8 m/s²) x (1/6) ≈ 1.63 m/s²
Given that the weight of an object is directly proportional to the gravitational force, the weight of an object on the moon would be substantially less than its weight on Earth. Thus, the weight of the bowling ball on the moon would be:
Weight on Moon = (Mass) x (1.63 m/s²) = 1/6 of its weight on Earth
Therefore, the weight of a bowling ball on the moon is 1/6 of its weight on Earth.
Question 24 Report
A force of 10N extends a spring of natural length 1m by 0.02m, calculate the length of the spring when the applied force is 40N.
Answer Details
To solve this problem, we will use Hooke's Law. Hooke's Law states that the force needed to extend or compress a spring by some distance is proportional to that distance. Mathematically, it is represented as:
F = k * x
where:
Firstly, we need to find the spring constant k. We know that a force of 10N extends the spring by 0.02m. Therefore, using Hooke's Law:
10N = k * 0.02m
From this, we can solve for k:
k = 10N / 0.02m = 500N/m
Now that we have determined the spring constant, let's calculate the extension caused by a force of 40N:
Using Hooke's Law again:
F = k * x
40N = 500N/m * x
Solving for x:
x = 40N / 500N/m = 0.08m
This means that the spring is extended by 0.08m when a force of 40N is applied. Therefore, the length of the spring (natural length plus extension) becomes:
1.00m + 0.08m = 1.08m
Thus, the **length** of the spring when the applied force is 40N is 1.08m.
Question 25 Report
The friction due to air mass can be reduced by
Answer Details
Friction due to air mass, also known as air resistance or drag, can be reduced by a concept called **streamlining**.
**Streamlining** refers to the shaping of an object in such a way that it allows air to flow smoothly around it, minimizing turbulence and reducing drag. When air flows smoothly over an object without much disturbance, there is less resistance, and the object can move more easily through the air.
Think of it like how a bullet or a fast-moving car is designed. They have a sleek, smooth shape that cuts through the air with minimal effort. This principle is applied in designing cars, airplanes, and even boats to enhance their efficiency and speed by reducing the friction with the air or water they move through.
Question 26 Report
A blacksmith heated a metal whose cubic expansivity is 3.9 x 10−6 K−1 . Calculate the area expansivity.
Answer Details
To find the area expansivity of a metal when given its cubic expansivity, you should understand the relationship between linear, area, and cubic expansivity.
Cubic expansivity (\( \beta \)) is defined as the fractional change in volume per change in temperature, and is given by the formula:
\[ \Delta V = \beta V \Delta T \]
Area expansivity (\( \alpha_{A} \)) corresponds to the fractional change in area per change in temperature and can be derived from the linear expansivity (\( \alpha \)). The relationship between these expansivities is as follows:
\[ \text{Area Expansivity (\( \alpha_{A} \))} = 2 \times \text{Linear Expansivity (\( \alpha \))} \]
The cubic expansivity (\( \beta \)) is related to the linear expansivity by:
\[ \text{Cubic Expansivity (\( \beta \))} = 3 \times \text{Linear Expansivity (\( \alpha \))} \]
Thus, based on these relationships, we can express the area expansivity in terms of the cubic expansivity:
\(\text{Area Expansivity (\( \alpha_{A} \))} = \frac{2}{3} \times \text{Cubic Expansivity (\( \beta \))}
Given that the cubic expansivity \( \beta \) is \( 3.9 \times 10^{-6} \, \text{K}^{-1} \):
The area expansivity can be calculated as follows:
\[ \text{Area Expansivity (\( \alpha_{A} \))} = \frac{2}{3} \times 3.9 \times 10^{-6} \, \text{K}^{-1} = 2.6 \times 10^{-6} \, \text{K}^{-1} \]
Therefore, the **correct answer** is **2.6 x 10^{-6} K^{-1}**.
Question 27 Report
Infra-red thermometers work by detecting the
Answer Details
Infra-red thermometers work by detecting the radiation from the body and converting it to temperature. These thermometers are designed to measure the infrared radiation, also known as heat radiation, emitted by objects. All objects with a temperature above absolute zero emit infrared radiation. The thermometer's sensor captures this radiation and converts it into an electrical signal that can be read as a temperature measurement. This method allows for quick, non-contact temperature readings, which is why infrared thermometers are often used in medical settings, industrial applications, and more.
Question 28 Report
When a charged ebonite rod is brought near a charged glass rod, there will be
Answer Details
When a charged ebonite rod is brought near a charged glass rod, there will be attraction. This is because charged objects obey the fundamental principle of electrostatics, which states that opposite charges attract each other while like charges repel each other.
An ebonite rod typically acquires a negative charge when rubbed with fur, as it gains electrons. In contrast, a glass rod usually acquires a positive charge when rubbed with silk, as it loses electrons. Therefore, when these two objects, one negatively charged and the other positively charged, are brought near each other, the opposite charges will attract.
Question 29 Report
What is the least possible error encountered when taking measurement with a metre rule?
Answer Details
A standard meter rule has markings that are usually every millimeter (1 mm). The least count, which is the smallest measurement that can be accurately read, is often 1 mm.
The least possible error is generally considered to be half of the smallest division, so it is ±0.05cm (or ±0.5mm).
Question 30 Report
At absolute zero temperature, the average velocity of the molecules
Answer Details
At absolute zero temperature, which is defined as 0 Kelvin or -273.15 degrees Celsius, the energy of molecular motion ceases. This means that the molecules theoretically have minimal energy, and hence, their motion stops entirely. Therefore, the average velocity of the molecules is zero. In reality, absolute zero is a theoretical limit, and it is practically unreachable, but it serves as a concept to help in understanding the behavior of molecules at extremely low temperatures. Thus, under this theoretical condition, the average motion of molecules would be nonexistent. In summary, the average velocity of the molecules at absolute zero is zero.
Question 31 Report
If the velocity ratio of a machine is 4, what does it mean?
Answer Details
The velocity ratio of a machine is a concept used to explain how much the machine is expected to amplify the input motion. If the velocity ratio of a machine is 4, it means that the distance moved by the effort is 4 times greater than the distance moved by the load.
To understand this concept better, consider what a machine does: it allows you to apply a small effort over a longer distance to move a heavy load over a shorter distance. In this scenario, if the velocity ratio is 4, then for every 4 meters (or units of distance) you exert effort, the load will move 1 meter (or unit of distance).
Question 32 Report
Rainbow is formed when sunlight undergoes
Answer Details
A rainbow is formed through a combination of three processes: reflection, refraction, and dispersion. Let's break down each process to understand how a rainbow forms:
1. Refraction: When sunlight enters a raindrop, it bends or changes direction. This bending of light is known as **refraction**. Different colors of sunlight bend by different amounts because they have different wavelengths.
2. Reflection: Once inside the raindrop, the light gets reflected off the inside surface of the drop. This reflection sends the light back out of the raindrop at different angles.
3. Dispersion: As the light exits the raindrop, it bends again (refraction). Because each color bends by a different amount, the sunlight is spread out into its component colors, creating a spectrum. This spreading into a spectrum is called **dispersion**.
All three processes contribute to the formation of a rainbow. The combination of **refraction, reflection, and dispersion** results in the beautiful arc of colors that we see in the sky.
Question 33 Report
The simple form of the lead acid accumulator often has a negative pole of
Answer Details
The simple form of the lead acid accumulator often has a negative pole of lead plate. In a lead-acid battery, the key components include two electrodes and an electrolyte. The **negative pole**, also known as the cathode during discharge, is typically made of **lead (Pb)**, which is in the form of a **lead plate**. When the battery is in use or discharging, this lead reacts with sulphuric acid (the electrolyte) to create lead sulfate.
To break it down further:
Thus, by analyzing the composition and reactions within a lead-acid battery, it is clear that the **negative pole** is made from a **lead plate**.
Question 34 Report
A practical application of total internal reflection is found in
Answer Details
A practical application of total internal reflection is found in fiber optics.
To understand this, let's break it down:
When light travels from one medium to another (such as from glass to air), it changes direction. This is known as refraction. However, there is a phenomenon called total internal reflection which occurs when light is traveling within a denser medium towards a less dense medium (like from glass to air) and hits the boundary at an angle greater than a certain critical angle. Instead of passing through, the light is completely reflected back into the denser medium.
Fiber optics technology makes use of this principle. In fiber optics, light is transmitted along the core of a thin glass or plastic fiber. The core is surrounded by another layer called the cladding. This cladding has a lower refractive index than the core, which facilitates total internal reflection. As a result, the light continuously reflects internally along the length of the fiber, allowing it to travel long distances with minimal loss.
This property is harnessed in various applications such as in high-speed telecommunication systems, medical equipment like endoscopes, and other technologies that require the transmission of data over long distances with high efficiency.
Question 35 Report
The quantity of heat required to melt ice of 0.2 kg whose specific latent heat is 3.4 x 105 J/Kg is
Answer Details
To determine the quantity of heat required to melt ice, we use the formula for latent heat:
Q = m × L,
where:
For this problem, we have:
Now, substitute these values into the formula:
Q = 0.2 kg × 3.4 × 105 J/kg
Calculate the product:
Q = 0.68 × 105 J
To express this in standard scientific notation, it can be rewritten as:
Q = 6.8 × 104 J
Thus, the quantity of heat required to melt 0.2 kg of ice is 6.8 × 104 J.
Question 36 Report
Bifocal lens is used to correct the eye defect of
Answer Details
Bifocal lenses are primarily used to correct the eye defect known as presbyopia. As people age, the lens of the eye naturally loses its flexibility, making it difficult to focus on objects that are close up. This condition is known as presbyopia. A bifocal lens is designed with two different optical powers to accommodate this need. The upper part of the lens is usually crafted for distance vision, while the lower segment is designed for near vision tasks, such as reading.
Astigmatism is a different eye condition caused by irregular curvature of the cornea or lens, resulting in blurred or distorted vision at all distances. This condition is typically corrected with cylindrical lenses rather than bifocals.
Hypermetropia, commonly known as farsightedness, is a condition where distant objects can be seen more clearly than near ones. Simple convex lenses are usually used for this correction.
Myopia, or nearsightedness, is a condition where nearby objects are seen clearly, while distant objects appear blurry. Concave lenses are generally used to correct this condition.
In summary, bifocal lenses are specifically designed to address the challenges of focusing at different distances simultaneously, making them ideal for managing presbyopia.
Question 37 Report
Answer Details
To understand when a vapor is considered saturated, it is crucial to consider the rates of two significant processes: evaporation and condensation. **Evaporation** is the process where liquid molecules escape into the vapor phase, and its rate is denoted as **y**. On the other hand, **condensation** is the process where vapor molecules return to the liquid phase, with its rate denoted as **x**.
A vapor is said to be **saturated** when the rate of evaporation of the liquid is equal to the rate of condensation of the vapor. In simpler terms, the number of molecules leaving the liquid to become vapor is exactly equal to the number of molecules returning from the vapor to the liquid.
In mathematical terms, this condition can be described as **x = y**. Under this condition, the system reaches a dynamic equilibrium, and the vapor pressure of the system is at its maximum for the given temperature. At this point, the vapor cannot accommodate any more molecules, and thus, the vapor is in a saturated state.
Question 38 Report
The food nutrient with the highest energy value is
Answer Details
Fat is the food nutrient with the highest energy value, providing 9 calories per gram, while carbohydrates and proteins provide 4 calories per gram.
Fat is the body's most concentrated source of energy, providing more than twice as much potential energy as carbohydrates or proteins.However, carbohydrates burn fastest in metabolism. Fats are a type of lipid. Lipids are a group of organic compounds that are insoluble in water but soluble in organic solvents. Fats are solid at room temperature, while oils are liquid at room temperature.
Therefore, the correct answer is option C.
Question 39 Report
The process by which plants loss water to the atmosphere is
Answer Details
The process by which plants lose water to the atmosphere is called transpiration.
Transpiration is a fundamental process in the life of a plant. During this process, water is absorbed by the roots from the soil and is then transported through the xylem vessels in the stem and leaves. Once in the leaves, water evaporates into the atmosphere from the surface of tiny pores known as stomata.
Here's a simple breakdown of how transpiration works:
Transpiration is crucial for a number of reasons:
Understanding transpiration is essential in fields like agriculture, where managing water resources efficiently can significantly impact plant growth and crop yield.
Question 40 Report
In a Hare's apparatus, the height of water and a liquid X are 0.3m and 0.5m respectively. The relative density of x is?
Answer Details
For Hare's apparatus
Relative density = hwhl
Given: height of liquid = 0.5cm, height of water = 0.3cm
Relative density = 0.30.5 = 0.6
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