Understanding the Electromagnetic Spectrum and Light Reflection
Electromagnetic Spectrum
The electromagnetic spectrum is the range of all types of electromagnetic radiation. Radiation is energy that travels and spreads out as it goes. The waves that form the electromagnetic spectrum are:
- Radio waves
- Television (TV) and FM radio waves
- Microwaves
- Infrared Radiation
- Visible Radiation
- UV Radiation
- X-Rays
- Gamma rays
Light Sources, Illuminated Bodies, and Propagation
All bodies that are light sources emit their own light.
Illuminated bodies are classified as:
- Opaque bodies
- Translucent bodies
- Transparent bodies
Propagation of Light
Light propagates in a straight line (this is called a straight-line light beam) and in all directions in a homogeneous medium.
When an opaque body is placed in front of a light source, a shadow occurs. When the darkness is not total, it’s called gloom.
Reflection of Light
Light reflection is a phenomenon that occurs when light rays strike a surface and change direction of propagation.
The elements involved in light reflection are:
- Incident Ray: The ray of light that reaches the surface.
- Reflected Ray: The ray of light that leaves the surface.
- Normal: An imaginary straight line perpendicular to the surface at the point of incidence.
- Angle of Incidence: The angle formed between the incident ray and the normal.
- Angle of Reflection: The angle formed by the reflected ray and the normal.
Laws of Reflection
The laws of reflection explain how light is reflected by a body:
- The angle between the incident ray and the surface normal equals the angle formed by the reflected ray with the surface normal.
- The incident ray and reflected ray are in the same plane.
Reflection on a perfectly smooth surface is called specular reflection.
Reflection on an irregular surface that reflects the rays in all directions is called diffuse reflection.
Mirrors
Mirrors are surfaces that reflect light rays that strike them. If parallel rays hit a mirror, the reflected rays also emerge parallel.
Mirrors create a specular reflection, which involves reversing the image; what is on the right of the object appears on the left in the image.
Mirrors are classified into flat and spherical mirrors.
Plane Mirrors
Plane mirrors are formed by a flat surface.
The elements involved when forming images on a plane mirror are:
- Real Zone: The area in front of the mirror.
- Virtual Zone: The area behind the mirror.
- Object: The body from which rays of light are drawn, affecting the mirror; it is always in the real zone.
- Image: The body found through the intersection of the reflected rays (real) or the extension of these rays (virtual).
Characteristics of Images in Plane Mirrors
- The image has the same size as the object.
- The image is formed behind the mirror (virtual image) and is the same distance from the mirror as the object.
- The image is laterally inverted.
Spherical Mirrors
Spherical mirrors are formed by a spherical surface.
There are two types of spherical mirrors:
- Concave Mirror: Spherical mirrors whose reflective surface is the inner spherical surface.
- Convex Mirror: Spherical mirrors whose reflective surface is the outer spherical surface.
Optical Elements of Spherical Mirrors
- Object: The body from which rays of light are drawn, affecting the mirror; it is always in the real zone.
- Image: The body found by the intersection of the reflected rays (real) or the extension of these rays (virtual).
- Real Zone: The area in front of the mirror.
- Virtual Zone: The area behind the mirror.
- Center of Curvature (C): The center of the sphere of the mirror.
- Vertex (A): The geometric center of the mirror.
- Optical Axis: The line connecting the center of curvature and the vertex.
- Focus (F): The point where all the reflected rays pass through the mirror that come from rays that are parallel to the main axis.