what is the principle behind optical fibers used in communication

ATI TEAS 7

TEAS 7 science practice

1. What is the principle behind optical fibers used in communication?

A. Reflection of light within the fiber
B. Refraction of light due to different densities within the fiber
C. Total internal reflection guiding light through the fiber core
D. Diffraction of light around bends in the fiber

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.

2. What is the primary function of B cells in the immune system?

A. Directly attacking and engulfing pathogens
B. Producing antibodies specific to a pathogen
C. Destroying infected body cells
D. All of the above

Correct answer: B

Rationale: B cells are a type of white blood cell that primarily functions by producing antibodies specific to a pathogen. These antibodies play a crucial role in marking pathogens for destruction by other immune cells. While B cells are essential for the immune response, they do not directly attack and engulf pathogens or destroy infected body cells. These functions are carried out by other immune cells like macrophages and cytotoxic T cells. Therefore, the correct answer is B, as it accurately reflects the primary role of B cells in the immune system.

3. What is the difference between active and passive immunity?

A. Active immunity is short-lived, while passive immunity is long-lasting.
B. Active immunity involves the body's own immune response, while passive immunity provides immediate protection through antibodies from another source.
C. Active immunity only protects against bacterial infections, while passive immunity works against both bacteria and viruses.
D. Passive immunity requires repeated vaccinations, while active immunity is a one-time process.

Correct answer: B

Rationale: Active immunity involves the body's own immune response, where the individual's immune system produces antibodies in response to exposure to a pathogen or vaccine. This type of immunity is long-lasting because the immune system 'remembers' the pathogen and can mount a rapid response upon re-exposure. In contrast, passive immunity provides immediate protection through the transfer of pre-formed antibodies from another source, such as through maternal antibodies crossing the placenta or receiving antibodies through an injection. Passive immunity is short-lived because the transferred antibodies eventually degrade and are not produced by the recipient's immune system. Choice A is incorrect because active immunity is generally long-lasting, as it involves the production of antibodies by the individual's immune system. Choice C is incorrect as both active and passive immunity can work against various pathogens, not limited to bacteria or viruses. Choice D is incorrect as passive immunity does not require repeated vaccinations but provides temporary protection through the transfer of antibodies from an external source.

4. Which body system is responsible for the transport of dissolved oxygen from the lungs to the spleen?

A. Immune
B. Endocrine
C. Respiratory
D. Cardiovascular

Correct answer: D

Rationale: The correct answer is the cardiovascular system (Option D). The cardiovascular system is responsible for transporting oxygenated blood from the lungs, where oxygen is absorbed, to various tissues and organs in the body, including the spleen. The immune system (Option A) is responsible for defending the body against infections and diseases. The endocrine system (Option B) regulates hormones and their effects on the body. The respiratory system (Option C) is responsible for the exchange of gases, such as oxygen and carbon dioxide, in the lungs.

5. Which type of lens focuses parallel light rays to a single point?

A. Concave lens
B. Convex lens
C. Cylindrical lens
D. Plano lens

Correct answer: B

Rationale: A convex lens focuses parallel light rays to a single point by causing them to converge. This lens is thicker in the center than at the edges, which helps in converging the light rays. Convex lenses are commonly used for tasks like magnification and focusing due to their ability to bring distant light rays to a single focal point. Choice A, the concave lens, diverges light rays rather than converging them, making it incorrect. Choice C, the cylindrical lens, is designed to focus light along one axis rather than converging parallel light rays to a single point. Choice D, the plano lens, has no curvatures to bend or focus light rays, so it does not converge parallel light rays.