TEAS 7 science practice

Correct Answer: C

Rationale: Optical fibers used in communication rely on the principle of total internal reflection guiding light through the fiber core. Total internal reflection occurs when light traveling through the core of the fiber is reflected back into the core due to the higher refractive index of the core compared to the cladding. This reflection ensures that the light remains confined within the core and propagates along the fiber without significant loss, allowing for efficient transmission of signals over long distances in optical communication systems. Choice A is incorrect because optical fibers do not primarily rely on simple reflection; instead, they utilize total internal reflection to guide light. Choice B is incorrect as the primary principle is not the refraction of light due to different densities within the fiber, but rather total internal reflection. Choice D is incorrect as diffraction is not the main principle behind optical fibers, which mainly rely on total internal reflection to guide light through the fiber core.

Correct Answer: D

Rationale: When a car is traveling at a constant speed on a straight road, it indicates that the forces acting on the car are balanced. In this scenario, there is no acceleration or deceleration, meaning the net force on the car is zero. If there was a net force present, it would cause the car to either accelerate or decelerate. Choices A, B, and C are incorrect because in a situation where a car is moving at a constant speed, the forces are balanced, and there is no unbalanced force acting in any specific direction.

Correct Answer: B

Rationale: The correct answer is the Mitral valve. The mitral valve is located between the left atrium and the left ventricle of the heart. Its function is to prevent the backflow of blood from the left ventricle into the left atrium during ventricular contraction. Choice A, the Tricuspid valve, is incorrect as it is located between the right atrium and right ventricle. Choice C, the Aortic valve, and Choice D, the Pulmonic valve, are also incorrect as they are involved in the circulation of blood leaving the heart rather than preventing backflow within the atria and ventricles.

Correct Answer: D

Rationale: The waste product of protein digestion is ammonia. Protein digestion breaks down proteins into amino acids, and during this process, ammonia is produced. Ammonia is toxic and needs to be converted into urea in the liver for excretion via urine. Glucose is a product of carbohydrate digestion, amino acids are building blocks of proteins, and fatty acids are the end products of fat digestion. Therefore, the correct answer is ammonia.

Correct Answer: B

Rationale: B) Splicing is the correct answer. Splicing is the process by which non-coding regions (introns) are removed from pre-mRNA, and the remaining coding regions (exons) are joined together to form mature mRNA. This modification occurs after transcription but before translation. A) Replication is incorrect as replication is the process by which DNA is copied to produce a new DNA molecule, not RNA modifications. C) Editing may involve RNA editing, but it is not commonly used to describe the modification of RNA molecules after transcription. D) Packaging is not the correct term as it refers to the condensation and organization of DNA into chromatin in eukaryotic cells, not the modification of RNA molecules.