Reflection of Light (Laws of Reflection, Plane and Curved Mirrors) - SS2 Physics Lesson Note
Reflection of light is the process by which light waves bounce off a surface after striking it. It plays a crucial role in our daily lives, enabling us to see objects and perceive our surroundings. The laws of reflection govern how light behaves during this process, and mirrors, both plane and curved, are commonly used to study and manipulate the reflection of light.
The laws of reflection state:
- The incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.
- The angle of incidence is equal to the angle of reflection.
These laws apply to both plane mirrors and curved mirrors.
Plane mirrors:
Plane mirrors have a flat, reflective surface. When light rays strike a plane mirror, they reflect off the mirror's surface. The reflection is specular, meaning that the angle of incidence is equal to the angle of reflection, and the reflected rays maintain their parallel nature. Images formed by plane mirrors are virtual, meaning they cannot be projected onto a screen. The size and distance of the image formed by a plane mirror are equal to the size and distance of the object.
Curved mirrors:
Curved mirrors include concave and convex mirrors, which have surfaces that are either inward or outward-curved, respectively. These mirrors exhibit different properties of reflection compared to plane mirrors.
Concave mirrors:
Concave mirrors are curved inward, and they converge light rays. When parallel light rays strike a concave mirror, they converge and meet at a point called the focal point. The distance from the mirror's surface to the focal point is called the focal length. The reflection of light in concave mirrors follows the laws of reflection, and the reflected rays can either diverge or converge depending on the location of the object relative to the mirror. Images formed by concave mirrors can be real or virtual, depending on the position of the object. Real images are formed when the object is placed beyond the focal point, while virtual images are formed when the object is placed between the mirror and the focal point.
Convex mirrors:
Convex mirrors are curved outward and diverge light rays. When parallel light rays strike a convex mirror, they diverge as if they are coming from a point behind the mirror, called the virtual focal point. The reflection of light in convex mirrors also follows the laws of reflection, and the reflected rays always diverge. Images formed by convex mirrors are always virtual, smaller in size, and located closer to the mirror than the actual object.
The study and understanding of reflection in mirrors are essential in various applications, such as optics, imaging systems, telescopes, and microscopy. Additionally, the principles of reflection are utilised in everyday objects like rear-view mirrors, makeup mirrors, and reflective surfaces used in lighting fixtures.
In summary, reflection of light occurs when light waves bounce off a surface, following the laws of reflection. Plane mirrors have flat reflective surfaces and produce virtual images, while curved mirrors, such as concave and convex mirrors, exhibit different reflective properties and can form real or virtual images depending on the object's position. The study of reflection and the use of mirrors have widespread applications in science, technology, and everyday life.