Reflection of Light
* Light travels in straight lines.
* A shiny or polished surface, such as a mirror, can change the direction of incident light.
* The bouncing of light by any smooth surface like a mirror, back into the same medium, is called reflection of light.
* The likeness of light by an object formed in a mirror due to reflection of light is called the image of the object.
* The image in a plan mirror is at the distance behind the mirror as the distance of the object in front of it.
* The image of an object formed in a plan mirror is left – right inversed. left – right inversed means that the image shows your right to appear as left, and left to appear as right.
An image formed by a plan mirror is:
* The same size as the object.
* Left – right inversed
* Erect
* Virtual
* Formed behind the mirror
* At the same distance behind the mirror as the distance of the object in front of the mirror.
* Images that cannot be captured on a screen are known as virtual images.
Light – Spherical Mirrors
* Spherical mirrors are cut and made from a hollow sphere.
* Spherical mirrors have curved reflecting surfaces hence, they are also known as curved mirrors.
There are two types of spherical mirrors depending upon the type of its reflecting surface:
* Concave mirrors
* Convex mirrors
* If the reflecting surface of a mirror is concave, it is called a concave mirror.
* If the reflecting surface of a mirror is convex, it is called a convex.
Uses of convex mirrors:
* Reflectors at sharp turns and tricky corners, in traffic as well as in parking lots
* Rear view mirrors in cars.
* Simple and handy security feature at ATMs.
* Surveillance mechanism at supermarkets and stores.
* An aid to camera mobile phone users for clicking self – portraits.
Uses of concave mirrors:
* By dentists to magnify the tooth.
* For shaving mirrors
* For solar heater or solar concentrators
* As reflectors in flashlights, headlights of cars and scooters.
* Images that cannot be captured on a screen are known as virtual images.
* Images that can be captured on a screen are known as real images.
Depending on the distance of an object from a concave mirror, the images formed by a concave mirror can be:
* Real or virtual
* Erect or Inverted
* Magnified or diminished
Depending on the distance of an object from a convex mirror, the images formed by a convex mirror are:
* Virtual
* Erect
* Diminished
Light – Reflection in Plane Mirrors
* Refection is b of bouncing back of light incidents incident on an object into the same medium through which it is the object.
* The path along which light travels is called a ray of light.
* A collection of light rays is called a beam of light.
Laws of Reflection:
* The angle of the incidence is always equal to the reflection.
* The incident ray, the normal at the point of incidence and the reflected ray lie in the same plane.
* The light ray from a source to the reflecting surface is called the incident ray.
* The light ray that reflects or bounces back from the reflecting surface is called the reflected ray.
* The line making an angle 90° with the line representing the mirror, at the point of incidence, is called the normal.
* The angle between the reflected ray and the normal is called the angle of refection.
* The angle of incidence is always equal to the angle of reflections.
The image of an object in a plan mirror is:
* Erect
* Of the same size as that of the object.
* Formed behind the mirror at the distance equal to that of the object from the plane mirror.
* Laterally inverted
* Images formed by a plan mirror cannot be obtained on a screen.
* Irregular or diffused reflection is reflection when a parallel beam of rays incident on an object are not reflected parallel to each other.
* In regular reflection, a set of incident rays parallel to each other are reflected from a very smooth surface as a set of parallel rays.
* Images are formed only from regular reflection.
* Objects that have light of their own are called luminous object and other that don’t are called illuminated objects.
* Multiple reflections of light rays from smooth surfaces result in formation of many images.
* The greater the angle between two plane mirrors inclined at the angle the lesser the number of images formed of an object placed between them.
* The formation of a rainbow is a natural phenomenon seen due to the dispersion of light.
Light – Reflection in Spherical Mirrors
* A spherical mirror is made from a part of a hollow sphere of glass.
* Focal length of a spherical mirror is half of its radius of curvature.
* A convex mirror reflects light from its outer spherical surface and has a silver coating on its inner surface.
* A concave mirror reflects light from its inner spherical surface and has a silver coating on its outer surface.
* In convex mirrors, the location of the object does not affect the characteristics of the image.
* The nature and size of the image in a concave mirror depends on relative position of the object from the mirror.
* The ratio of the height of an image to the height of an object is called line at magnification. Magnification can be unity, greater than one, or less than one.
* The mirror formula defined the relationship between the focal length of the mirror, the object distance and the image distance.
The formula is:
\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
