Fundamental Physics Concepts Explained

Law of Gravitation

Every object in the universe that has mass exerts a gravitational attraction on other objects with mass, regardless of the distance between them. According to this law, more massive objects exert a greater force of attraction. In parallel, the closer objects are, the greater the force, following an inverse square law.

Considering two masses whose size is small compared with the distance that separates them, we can summarize this in an equation or law that states that the force exerted by a given object with mass m1 on one with mass m2 is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.

A force is central where the position vector r is parallel to the force vector F. The moment of force M = r'F = 0. Concerning the relationship between the forces acting on the particle and angular momentum (angular momentum theorem), it concludes that:

Operation of a Magnifying Glass

The operation of a lens is represented in the ray pattern of Fig. The object is placed on the focus so the image is formed at infinity. Finally, the image formation is performed by the eye, and the size on the retina is greater than that formed without a magnifier.

Young's Experiment

Young's experiment was conducted in an attempt to discern the corpuscular or wave nature of light. Young found a pattern of interference of light from a distant source to be diffracted in passing through two slits, a result that contributed to the theory of the wave nature of light. The experiment has been considered fundamental in demonstrating wave-particle duality, a property of quantum mechanics. The experiment can also be done with electrons, atoms, or neutrons, producing interference patterns similar to those obtained when performed with light, showing, therefore, the dual wave-particle behavior of matter.

Laws of Reflection and Refraction

Reflection is the change in direction of a ray or a wave that occurs at the boundary between two media, so that the ray or wave returns to the initial medium. Common examples are the reflection of light, sound, and waves in water.

Laws of regular reflection (specular reflection): When the reflecting surface is very smooth, specular or regular reflection of light occurs. For this case, the laws of reflection are as follows:

• The incident ray, the reflected ray, and the normal, should be in the same plane (same medium) with respect to the reflecting surface at the point of incidence.
• The angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal.

Refraction is the change of direction experienced by a wave as it passes from one medium to another material. It only occurs if the wave is incident obliquely on the surface separating the two media and if they have different refractive indices. Refraction arises from the change in velocity experienced by the wave. An example of this phenomenon is when a pencil is immersed in a glass of water: the pencil appears broken.