Final answer:
Both the assertion that electromagnetic radiations exert pressure and the reason that they carry momentum and energy are true. The reason is indeed the correct explanation for the assertion, as the momentum carried by electromagnetic waves is responsible for the exertion of force on objects, leading to the observed pressure. Option A is the correct answer.
Step-by-step explanation:
The student is asking about the connection between electromagnetic radiation and its ability to exert pressure on objects. This is a concept covered in physics, primarily when discussing the properties of light and electromagnetic waves. According to physics, not only does electromagnetic radiation carry energy, it also carries momentum. When electromagnetic waves interact with an object, they can exert forces on the charged particles within that object. These forces result in radiation pressure, which can either increase if the radiation is reflected, or be less if it is absorbed.
The assertion in the question is true: electromagnetic radiations indeed exert pressure. This is a well-documented phenomenon in physics and is observable in various contexts, such as solar sails in space probes. The reason given that electromagnetic waves carry both momentum and energy is also true and serves as an accurate explanation for the assertion. When electromagnetic waves exert a force upon an object, e.g., during absorption or reflection, this can be seen as a consequence of the momentum they carry. Hence, the correct explanation of why electromagnetic radiation can exert pressure is indeed because it carries momentum and energy.
Moving forward with our explanation that the radiation pressure from electromagnetic waves on a perfectly reflecting surface would be twice as large as one that is absorbed can be understood by considering the momentum transfer. When radiation is reflected, the reversal of its momentum upon the reflecting surface exerts a greater force than if the radiation is simply absorbed. Applying this principle to astronomical contexts, radiation pressure, although very small, can have significant effects such as on the tails of comets or the trajectory of solar system bodies when considering very long time scales.
Thus, we can conclude that the correct option is (a) Both assertion and reason are true and reason is the correct explanation of assertion.