a) Red traffic signals can be seen from a very long distance:
• The reason red traffic signals are visible from a long distance is because of the wavelength of the color red. Red light has a longer wavelength compared to other colors in the visible spectrum. Longer wavelengths can penetrate atmospheric particles and scatter less than shorter wavelengths. This phenomenon is known as Rayleigh scattering.

• In practical terms, red light is less likely to be scattered by dust, water droplets, and other particles in the atmosphere. This property allows red light to travel a longer distance with less attenuation, making red objects, including traffic signals, more visible from afar.

b) Stars appear to be slightly higher than their actual position:

• This phenomenon is known as stellar aberration and is a result of the Earth’s motion through space. As the Earth moves along its orbit around the Sun, it causes a change in the direction of starlight due to the combination of the Earth’s velocity and the finite speed of light.

• Stellar aberration causes stars to appear slightly displaced from their actual position in the sky. The effect is similar to raindrops hitting a moving car windshield. If the car is moving, raindrops will appear to come from a direction slightly in front of their actual path. Similarly, the motion of Earth causes starlight to be slightly shifted in the direction of the Earth’s orbital motion.

The angle of displacement is tiny, and it does not affect the overall appearance of the stars to the naked eye. However, precise measurements and observations by astronomers take this phenomenon into account to accurately determine the positions of celestial objects.

a. Genes present in the F1 generation:
In the given cross, tall pea plants (TT) were crossed with short pea plants (tt). The F1 generation will have the genotype Tt. Each pea plant in the F1 generation inherits one allele from each parent, and since the tall trait is dominant (T), the presence of at least one dominant allele (T) results in a tall phenotype. Therefore, the set of genes present in the F1 generation is Tt.

b. Reason for only tall plants in F1 progeny:
In Mendelian genetics, when a dominant allele is present, it masks the effect of the recessive allele. In this case, “T” is the allele for tallness (dominant), and “t” is the allele for shortness (recessive). The genotype of the F1 plants is Tt, where the dominant allele “T” determines the tall phenotype. The presence of even one dominant allele results in the expression of the dominant trait, so all plants in the F1 generation appear tall.

c. Genotype and phenotype of the F2 generation:
When the F1 plants (Tt) are self-pollinated, the possible combinations of alleles during gamete formation can lead to different genotypes in the F2 generation. The possible genotypes and phenotypes, along with their ratios, can be determined using a Punnett square or the multiplication rule.

The possible genotypes in the F2 generation are:
• TT (tall)
• Tt (tall)
• Tt (tall)
• tt (short)
The expected phenotypic ratio in the F2 generation is 1:2:1 for tall:tall:short.
Now, if a total of 800 plants are produced in the F2 generation, you can calculate the expected number of plants for each phenotype:

Calculation Diagram:

Therefore, in the F2 generation, you would expect 600 tall plants, 200 short plants, and no medium-height plants. The genotype of the tall plants could be either TT or Tt.

In an asexually reproducing species, traits are passed on to offspring through direct replication of the genetic material of the parent. Unlike sexual reproduction, where genetic diversity arises through recombination, asexual reproduction involves the transmission of identical genetic material from one generation to the next.

Given that trait X exists in only 5% of the population, while trait Y exists in 70% of the population, it’s reasonable to infer that trait Y is likely to have arisen earlier. Here’s the reasoning:
• Stability of Trait X: Trait X being present in only 5% of the population suggests that it may not have spread as widely or as quickly. It could be a relatively new mutation or a less advantageous trait.
• Widespread Presence of Trait Y: Trait Y, on the other hand, being present in 70% of the population, indicates that it has had more time to spread and become prevalent. Traits that confer a selective advantage, promote survival, or enhance reproduction are more likely to become widespread in a population over time.
• Selection and Replication: In asexually reproducing species, the traits that offer a survival or reproductive advantage are more likely to be passed on to a larger proportion of the population with each generation. Traits that enhance an organism’s ability to survive and reproduce tend to become more prevalent over time.

In summary, the higher prevalence of trait Y in the population suggests that it is likely to have arisen earlier and had more time to spread through successive generations, possibly due to providing some selective advantage in the particular environment or conditions of the population.

The time it takes to boil water in an electric kettle is influenced by several factors, including the power of the heating element, the initial temperature of the water, and the efficiency of the kettle. Let’s focus on the impact of the length of the heating element.
The power (P) of the heating element is given by the formula:
P = V2/R
where:
P is power,
V is voltage, and
R is resistance.
The heating effect, which determines how quickly the water heats up, is given by the formula:
H = I2.R.t
where:
H is the heating effect,
I is current,
R is resistance, and
t is time.

The resistance (R) of the heating element is directly proportional to its length (L). Therefore, if the student wants to reduce the boiling time, he should aim to increase the power of the heating element, and subsequently, the heating effect.

To achieve this without changing the voltage or current (which are typically fixed by the mains supply), the student should decrease the resistance of the heating element. Since resistance is directly proportional to the length of the heating element, reducing the length of the heating element will decrease its resistance.
In conclusion, to reduce the boiling time of water, the student should decrease the length of the heating element.

Corrosion refers to the gradual degradation or destruction of a material, usually a metal or alloy, due to chemical or electrochemical reactions with its environment. The most common form of corrosion is the rusting of iron or steel, where the metal reacts with oxygen and water to form iron oxide, commonly known as rust.

Corrosion can take various forms depending on the material involved and the specific environmental conditions. Some common types of corrosion include:

Uniform Corrosion: This is a general attack on the surface of the material, resulting in a relatively even loss of material over the entire exposed area.

Galvanic Corrosion: This occurs when two different metals are in contact with each other in the presence of an electrolyte (such as moisture). The less noble (more reactive) metal corrodes preferentially.

Pitting Corrosion: This is characterized by the localized formation of small pits or craters on the metal surface. It can be more damaging than uniform corrosion because it concentrates the attack in specific areas.

Crevice Corrosion: Occurs in confined spaces or crevices, where the lack of access to fresh oxygen or the accumulation of corrosive substances can lead to localized corrosion.

Stress Corrosion Cracking (SCC): This is a type of corrosion that occurs in the presence of both tensile stress and a corrosive environment. It can lead to the sudden failure of materials under stress.

Corrosion is a significant concern in various industries, as it can compromise the structural integrity and functionality of materials and equipment. Preventive measures, such as protective coatings, corrosion-resistant alloys, and proper maintenance practices, are often employed to mitigate the impact of corrosion.